It is rightfully considered one of the significant inventions of the 20th century. invention of the transistor, which replaced vacuum tubes.

For a long time, lamps were the only active component of all radio-electronic devices, although they had many disadvantages. First of all, these are high power consumption, large dimensions, short service life and low mechanical strength. These shortcomings were felt more and more acutely as electronic equipment improved and became more complex.

A revolutionary revolution in radio engineering occurred when outdated lamps were replaced by semiconductor amplification devices - transistors, devoid of all the mentioned disadvantages.

The first functional transistor was born in 1947, thanks to the efforts of employees of the American company Bell Telephone Laboratories. Their names are now known throughout the world. These are scientists - physicists W. Shockley, D. Bardeen and W. Brighten. Already in 1956, all three were awarded the Nobel Prize in Physics for this invention.

But, like many great inventions, the transistor was not noticed immediately. Only one of the American newspapers mentioned that Bell Telephone Laboratories demonstrated a device it had created called a transistor. It was also said there that it can be used in some areas of electrical engineering instead of vacuum tubes.

The transistor shown was in the form of a small metal cylinder 13 mm long and was demonstrated in a receiver that did not have vacuum tubes. In addition, the company assured that the device can be used not only for amplification, but also for generating or converting an electrical signal.

Rice. 1. First transistor

Rice. 2. John Bardeen, William Shockley and Walter Brattain. They shared the 1956 Nobel Prize for their collaboration in developing the world's first operational transistor in 1948.

But the capabilities of the transistor, like many other great discoveries, were not immediately understood and appreciated. To generate interest in the new device, Bell heavily advertised it at seminars and in articles, and provided licenses for its production to everyone.

Manufacturers of electronic tubes did not see the transistor as a serious competitor, because it was impossible to immediately, in one fell swoop, discount the thirty-year history of producing tubes of several hundred designs, and multi-million dollar investments in their development and production. Therefore, the transistor did not enter electronics so quickly, since the era of vacuum tubes was still ongoing.

Rice. 3. Transistor and vacuum tube

First steps to semiconductors

Since ancient times, electrical engineering has used mainly two types of materials - conductors and dielectrics (insulators). Metals, salt solutions, and some gases have the ability to conduct current. This ability is due to the presence of free charge carriers - electrons - in conductors. In conductors, electrons are quite easily separated from the atom, but those metals that have low resistance (copper, aluminum, silver, gold) are most suitable for transmitting electrical energy.

Insulators are substances with high resistance; their electrons are very tightly bound to the atom. These are porcelain, glass, rubber, ceramics, plastic. Therefore, there are no free charges in these substances, which means there is no electric current.

Here it is appropriate to recall the formulation from physics textbooks that electric current is the directed movement of electrically charged particles under the influence of an electric field. In insulators there is simply nothing to move under the influence of an electric field.

However, in the process of studying electrical phenomena in various materials, some researchers managed to “feel” semiconductor effects. For example, the first crystal detector (diode) was created in 1874 by the German physicist Karl Ferdinand Braun based on the contact of lead and pyrite. (Pyrite is iron pyrite; when it hits the chair, a spark is struck, which is why it got its name from the Greek “pir” - fire). Later, this detector successfully replaced the coherer in the first receivers, which significantly increased their sensitivity.

In 1907, Boeddeker, while studying the conductivity of copper iodide, discovered that its conductivity increases 24 times in the presence of iodine impurities, although iodine itself is not a conductor. But all these were random discoveries that could not be scientifically substantiated. Systematic study of semiconductors began only in 1920 - 1930.

In the early days of transistor production, the main semiconductor was germanium (Ge). In terms of energy consumption, it is very economical, the unlocking voltage of its pn junction is only 0.1 ... 0.3 V, but many parameters are unstable, so silicon (Si) came to replace it.

The temperature at which germanium transistors operate is no more than 60 degrees, while silicon transistors can continue to operate at 150. Silicon, as a semiconductor, is superior to germanium in other properties, primarily in frequency.

In addition, the reserves of silicon (ordinary sand on the beach) in nature are limitless, and the technology for its purification and processing is simpler and cheaper than the element germanium, which is rare in nature. The first silicon transistor appeared shortly after the first germanium transistor - in 1954. This event even gave rise to the new name “silicon age”, not to be confused with the stone age!

Rice. 4. Evolution of transistors

Microprocessors and semiconductors. Decline of the “Silicon Age”

Have you ever wondered why recently almost all computers have become multi-core? The terms dual-core or quad-core are on everyone's lips. The fact is that increasing the performance of microprocessors by increasing the clock frequency and increasing the number of transistors in one package has almost reached the limit for silicon structures.

An increase in the number of semiconductors in one package is achieved by reducing their physical dimensions. In 2011, INTEL already developed a 32 nm process technology, in which the transistor channel length is only 20 nm. However, such a reduction does not bring a noticeable increase in clock frequency, as was the case up to 90 nm technologies. It is absolutely clear that it is time to move to something fundamentally new.

1956 In the Stockholm concert hall, three American scientists John Bardeen, William Shockley and Walter Brattain receive the Nobel Prize “for their research into semiconductors and the discovery of the transistor effect” - a real breakthrough in the field of physics. From now on, their names are forever inscribed in world science. But more than 15 years earlier, at the beginning of 1941, a young Ukrainian scientist Vadim Lashkarev experimentally discovered and described in his article a physical phenomenon, which, as it turned out, was subsequently called the p-n junction (p-positive, n-negative). In his article, he also revealed the injection mechanism - the most important phenomenon on the basis of which semiconductor diodes and transistors operate.

Officially, the history of the transistor goes like this: the first press report about the appearance of a semiconductor transistor amplifier appeared in the American press in July 1948. Its inventors are American scientists Bardeen and Brattain. They took the path of creating a so-called point-point transistor based on an n-type germanium crystal. They obtained their first encouraging result at the end of 1947. However, the device behaved unstable, its characteristics were unpredictable, and therefore the point-point transistor did not receive practical use.

A breakthrough occurred in 1951, when William Shockley created his more reliable planar n-p-n transistor, which consisted of three layers of n, p and n type germanium, with a total thickness of 1 cm. Within a few years, the significance of the invention of American scientists became obvious, and they were awarded the Nobel Prize.

Long before this, even before the start of the Great Patriotic War in 1941, Lashkarev conducted a series of successful experiments and discovered the p-n junction and revealed the mechanism of electron-hole diffusion, on the basis of which, under his leadership in the early 50s, the first ones were created in Ukraine (then part of the USSR) semiconductor triodes - transistors.

In scientific terms, a pn junction is a region of space at the junction of two p- and n-type semiconductors, in which a transition from one type of conductivity to another occurs. The electrical conductivity of a material depends on how tightly the nuclei of its atoms hold electrons. Thus, most metals are good conductors because they have a huge number of electrons weakly bound to the atomic nucleus, which are easily attracted by positive charges and repelled by negative ones. Moving electrons are the carriers of electric current. On the other hand, insulators do not allow current to pass through, since the electrons in them are tightly bound to the atoms and do not respond to the influence of an external electric field.

Semiconductors behave differently. Atoms in semiconductor crystals form a lattice, the outer electrons of which are bound by chemical forces. In their pure form, semiconductors are similar to insulators: they either conduct current poorly or do not conduct at all. But as soon as a small number of atoms of certain elements (impurities) are added to the crystal lattice, their behavior changes dramatically.

In some cases, impurity atoms bond with semiconductor atoms, forming extra electrons; the excess free electrons give the semiconductor a negative charge. In other cases, impurity atoms create so-called “holes” that can “absorb” electrons. Thus, a shortage of electrons occurs and the semiconductor becomes positively charged. Under the right conditions, semiconductors can conduct electrical current. But unlike metals, they conduct it in two ways. A negatively charged semiconductor tends to get rid of excess electrons; this is n-type conductivity (from negative). The charge carriers in semiconductors of this type are electrons. On the other hand, positively charged semiconductors attract electrons, filling the “holes.” But when one “hole” is filled, another appears nearby - abandoned by the electron. Thus, the “holes” create a flow of positive charge, which is directed in the direction opposite to the movement of electrons. This is p-type conductivity (from positive - positive). In both types of semiconductors, so-called non-majority charge carriers (electrons in p-type semiconductors and “holes” in n-type semiconductors) support the current in the direction opposite to the movement of the majority charge carriers.

By introducing impurities into germanium or silicon crystals, semiconductor materials with desired electrical properties can be created. For example, the introduction of a small amount of phosphorus generates free electrons, and the semiconductor acquires n-type conductivity. Adding boron atoms, on the other hand, creates holes and the material becomes a p-type semiconductor.

Later it turned out that a semiconductor into which impurities are introduced acquires the property of passing electric current, i.e. has conductivity, the value of which can, under a certain influence, vary within wide limits.

When a method was found in the USA to carry out such an effect electrically, the transistor (from the original name transresistor) appeared. The fact that in 1941 Lashkarev published the results of his discoveries in the articles “Study of barrier layers using the thermal probe method” and “The influence of impurities on the valve photoelectric effect in cuprous oxide” (co-authored with his colleague K.M. Kosonogova) was not due to wartime came to the attention of the scientific world. Presumably, the outbreak of the Cold War and the Iron Curtain that descended on the Soviet Union played a role in the fact that Lashkarev never became a Nobel laureate. By the way, Lashkarev, while in Siberia during the war, developed cuprox diodes that were used in army radio stations and achieved their industrial production.

In addition to the first two works, Lashkarev, in collaboration with V.I. Lyashenko, published the article “Electronic states on the surface of a semiconductor” in 1950, which described the results of studies of surface phenomena in semiconductors, which became the basis for the operation of integrated circuits based on field-effect transistors.

In the 50s, Lashkarev also managed to solve the problem of mass rejection of germanium single crystals. He formulated the technical requirements for this element in a new way, since the previous ones were unjustifiably overstated. Thorough research carried out by Lashkarev and Miseluk at the Institute of Physics of the Academy of Sciences of the Ukrainian SSR in Kyiv showed that the already achieved level of germanium single crystal technology made it possible to create point diodes and triodes with the necessary characteristics. This made it possible to accelerate the industrial production of the first germanium diodes and transistors in the former USSR.

Thus, it was under the leadership of Lashkarev in the early 50s that the production of the first point-point transistors was organized in the USSR. Formed by V.E. Lashkarev's scientific school in the field of semiconductor physics becomes one of the leading in the USSR. Recognition of outstanding results was the creation in 1960 of the Institute of Semiconductors of the Academy of Sciences of the Ukrainian SSR, which was headed by V.E. Lashkarev.

“The time will come when on this crystal that Vadim Evgenievich showed us, it will be possible to place an entire computer!” , - predicted academician Sergei Lebedev, who created the first computer in continental Europe - MESM. And so it happened. But this happened more than twenty years later, when large LSI integrated circuits appeared, containing tens and hundreds of thousands of transistors on a chip, and later, ultra-large VLSI integrated circuits with many millions of components on a chip, which opened the way for man to the information era.

PYATIGORSK STATE TECHNOLOGICAL UNIVERSITY

DEPARTMENT OF MANAGEMENT AND INFORMATION IN TECHNICAL SYSTEMS

ABSTRACT

"History of the development of transistors"

Completed:

Student gr. UITS-b-101

Sergienko Victor

Pyatigorsk, 2010

Introduction

Transistor (from the English transfer - transfer and resistance - resistance or transconductance - active interelectrode conductivity and varistor - variable resistance) is an electronic device made of semiconductor material, usually with three terminals, allowing input signals to control the current in an electrical circuit. Typically used to amplify, generate and convert electrical signals.

The current in the output circuit is controlled by changing the input voltage or current. A small change in input quantities can lead to a significantly larger change in output voltage and current. This amplifying property of transistors is used in analog technology (analog TV, radio, communications, etc.).

Currently, analog technology is dominated by bipolar transistors (BT) (the international term is BJT, bipolar junction transistor). Another important branch of electronics is digital technology (logic, memory, processors, computers, digital communications, etc.), where, on the contrary, bipolar transistors are almost completely replaced by field-effect ones.

All modern digital technology is built mainly on field-effect MOS (metal-oxide-semiconductor) transistors (MOSFETs), as they are more economical elements compared to BT. Sometimes they are called MIS (metal-dielectric-semiconductor) transistors. The international term is MOSFET (metal-oxide-semiconductor field effect transistor). Transistors are manufactured using integrated technology on a single silicon crystal (chip) and form an elementary “building block” for constructing logic, memory, processor, etc. chips. The dimensions of modern MOSFETs range from 90 to 32 nm. One modern chip (usually 1-2 cm² in size) accommodates several (still only a few) billion MOSFETs. Over the course of 60 years, there has been a decrease in the size (miniaturization) of MOSFETs and an increase in their number on one chip (degree of integration); in the coming years, a further increase in the degree of integration of transistors on a chip is expected (see Moore’s Law). Reducing the size of the MOPT also leads to increased processor speed, reduced power consumption and heat dissipation.

Story

The first patents on the operating principle of field-effect transistors were registered in Germany in 1928 (in Canada, October 22, 1925) in the name of the Austro-Hungarian physicist Julius Edgar Lilienfeld. In 1934, German physicist Oskar Heil patented the field-effect transistor. Field-effect transistors (in particular, MOS transistors) are based on a simple electrostatic field effect; in physics they are significantly simpler than bipolar transistors, and therefore they were invented and patented long before bipolar transistors. However, the first MOSFET, which forms the basis of the modern computer industry, was manufactured later than the bipolar transistor, in 1960. Only in the 90s of the 20th century did MOS technology begin to dominate over bipolar technology.

In 1947, William Shockley, John Bardeen and Walter Brattain at Bell Labs first created a working bipolar transistor, demonstrated on December 16. On December 23, the official presentation of the invention took place and this date is considered the day of the invention of the transistor. According to manufacturing technology, it belonged to the class of point-point transistors. In 1956, they were awarded the Nobel Prize in Physics "for their research into semiconductors and their discovery of the transistor effect." Interestingly, John Bardeen was soon awarded the Nobel Prize for the second time for creating the theory of superconductivity.

Vacuum tubes were later replaced by transistors in most electronic devices, revolutionizing the creation of integrated circuits and computers.

Bell needed a name for the device. The names "semiconductor triode", "Solid Triode", "Surface States Triode", "crystal triode" and "Iotatron" were suggested, but the word "transistor", proposed by John R. . Pierce), won the internal vote.

The name "transistor" originally referred to voltage-controlled resistors. In fact, a transistor can be thought of as a kind of resistance regulated by the voltage at one electrode (in field-effect transistors, by the voltage between the gate and the source, in bipolar transistors, by the voltage between the base and emitter).

Classification of transistors

Bipolar transistor- a three-electrode semiconductor device, one of the types of transistor. The electrodes are connected to three successively arranged semiconductor layers with alternating types of impurity conductivity. According to this method of alternation, npn and pnp transistors are distinguished (n (negative) - electronic type of impurity conductivity, p (positive) - hole type). In a bipolar transistor, unlike other varieties, the main carriers are both electrons and holes (from the word “bi” - “two”).

The electrode connected to the central layer is called the base, the electrodes connected to the outer layers are called the collector and emitter. In the simplest diagram, the differences between collector and emitter are not visible. In reality, the main difference between the collector is the larger area of ​​the p-n junction. In addition, a thin base thickness is absolutely necessary for the transistor to operate.

The bipolar point transistor was invented in 1947, and over the following years it established itself as a fundamental element for the manufacture of integrated circuits using transistor-transistor, resistor-transistor, and diode-transistor logic.

The first transistors were made on the basis of germanium. Currently, they are made mainly from silicon and gallium arsenide. The latter transistors are used in high-frequency amplifier circuits. A bipolar transistor consists of three differently doped semiconductor zones: emitter E, base B and collector C. Depending on the type of conductivity of these zones, NPN (emitter - n-semiconductor, base - p-semiconductor, collector - n-semiconductor) and PNP are distinguished. transistors. Conductive contacts are connected to each of the zones. The base is located between the emitter and collector and is made of a lightly doped semiconductor with high resistance. The total base-emitter contact area is significantly smaller than the collector-base contact area, so a general bipolar transistor is an asymmetrical device (it is impossible to swap the emitter and collector by changing the connection polarity and resulting in a bipolar transistor absolutely similar to the original one).

In the active operating mode, the transistor is turned on so that its emitter junction is biased in the forward direction (open), and the collector junction is biased in the opposite direction. For definiteness, let’s consider an npn transistor; all reasoning is repeated in exactly the same way for the case of a pnp transistor, with the word “electrons” replaced by “holes”, and vice versa, as well as with all voltages replaced with opposite signs. In an NPN transistor, electrons, the main current carriers in the emitter, pass through the open emitter-base junction (injected) into the base region. Some of these electrons recombine with the majority charge carriers in the base (holes), while some diffuse back into the emitter. However, because the base is made very thin and relatively lightly doped, most of the electrons injected from the emitter diffuse into the collector region. The strong electric field of the reverse-biased collector junction captures electrons (remember that they are minority carriers in the base, so the junction is open for them) and carries them into the collector. The collector current is thus practically equal to the emitter current, with the exception of a small recombination loss in the base, which forms the base current (Ie = Ib + Ik). The coefficient α connecting the emitter current and the collector current (Iк = α Iе) is called the emitter current transfer coefficient. The numerical value of the coefficient α is 0.9 - 0.999. The higher the coefficient, the more efficiently the transistor transmits current. This coefficient depends little on the collector-base and base-emitter voltages. Therefore, over a wide range of operating voltages, the collector current is proportional to the base current, the proportionality coefficient is equal to β = α / (1 − α) = (10..1000). Thus, by varying a small base current, a much larger collector current can be controlled. The levels of electrons and holes are approximately equal.

Field-effect transistor- a semiconductor device in which the current changes as a result of the action of a perpendicular current in the electric field created by the input signal.

The flow of operating current in a field-effect transistor is caused by charge carriers of only one sign (electrons or holes), therefore such devices are often included in the broader class of unipolar electronic devices (as opposed to bipolar).

History of the creation of field-effect transistors

The idea of ​​an insulated gate field effect transistor was proposed by Lilienfeld in 1926-1928. However, objective difficulties in implementing this design made it possible to create the first working device of this type only in 1960. In 1953, Dakey and Ross proposed and implemented another design of a field-effect transistor - with a control p-n junction. Finally, a third FET design, the Schottky barrier FET, was proposed and implemented by Mead in 1966.

Field-effect transistor circuits

A field-effect transistor can be connected in one of three main circuits: with a common source (CS), a common drain (OC) and a common gate (G).

In practice, a circuit with an OE is most often used, similar to a circuit with a bipolar transistor with an OE. A common source cascade gives a very large current and power amplification. The scheme with OZ is similar to the scheme with OB. It does not provide current amplification, and therefore the power amplification in it is many times less than in the OI circuit. The OZ cascade has a low input impedance, and therefore has limited practical use.

Classification of field effect transistors

Based on their physical structure and operating mechanism, field-effect transistors are conventionally divided into 2 groups. The first is formed by transistors with a control p-n junction or metal-semiconductor junction (Schottky barrier), the second is formed by transistors with control through an insulated electrode (gate), the so-called. MIS transistors (metal - dielectric - semiconductor).

Transistors with control p-n junction

A field-effect transistor with a control p-n junction is a field-effect transistor whose gate is isolated (that is, electrically separated) from the channel by a p-n junction biased in the opposite direction.

Such a transistor has two non-rectifying contacts to the region through which the controlled current of the main charge carriers passes, and one or two control electron-hole junctions biased in the opposite direction (see Fig. 1). When the reverse voltage changes at the p-n junction, its thickness and, consequently, the thickness of the region through which the controlled current of the main charge carriers passes changes. The region, the thickness and cross-section of which is controlled by an external voltage at the control p-n junction and through which a controlled current of the main carriers passes, is called a channel. The electrode from which the main charge carriers enter the channel is called the source. The electrode through which the main charge carriers leave the channel is called a drain. The electrode used to regulate the cross-section of the channel is called a gate.

The electrical conductivity of the channel can be either n- or p-type. Therefore, based on the electrical conductivity of the channel, field-effect transistors with an n-channel and a p-channel are distinguished. All polarities of the bias voltages applied to the electrodes of the n- and p-channel transistors are opposite.

Control of the drain current, that is, the current from an external relatively powerful power source in the load circuit, occurs when the reverse voltage changes at the p-n junction of the gate (or at two p-n junctions simultaneously). Due to the smallness of the reverse currents, the power required to control the drain current and consumed from the signal source in the gate circuit turns out to be negligibly small. Therefore, a field-effect transistor can provide amplification of electromagnetic oscillations both in power and in current and voltage.

Thus, the field-effect transistor is similar in principle to a vacuum triode. The source in a field-effect transistor is similar to the cathode of a vacuum triode, the gate is like a grid, and the drain is like an anode. But at the same time, a field-effect transistor differs significantly from a vacuum triode. Firstly, the field-effect transistor does not require heating the cathode to operate. Secondly, any of the functions of source and drain can be performed by each of these electrodes. Thirdly, field-effect transistors can be made with both an n-channel and a p-channel, which makes it possible to successfully combine these two types of field-effect transistors in circuits.

A field-effect transistor differs from a bipolar transistor, firstly, in its operating principle: in a bipolar transistor, the output signal is controlled by the input current, and in a field-effect transistor, by the input voltage or electric field. Secondly, field-effect transistors have significantly higher input resistances, which is associated with the reverse bias of the p-n junction of the gate in the type of field-effect transistors under consideration. Thirdly, field-effect transistors can have a low noise level (especially at low frequencies), since field-effect transistors do not use the phenomenon of injection of minority charge carriers and the field-effect transistor channel can be separated from the surface of the semiconductor crystal. The processes of carrier recombination in the p-n junction and in the base of the bipolar transistor, as well as generation-recombination processes on the surface of the semiconductor crystal, are accompanied by the appearance of low-frequency noise.

Insulated gate transistors (MIS transistors)

An insulated gate field-effect transistor is a field-effect transistor whose gate is electrically separated from the channel by a dielectric layer.

In a semiconductor crystal with a relatively high resistivity, which is called a substrate, two heavily doped regions with the opposite type of conductivity relative to the substrate are created. Metal electrodes are applied to these areas - source and drain. The distance between the heavily doped source and drain regions can be less than a micron. The surface of the semiconductor crystal between the source and drain is covered with a thin layer (about 0.1 μm) of dielectric. Since the initial semiconductor for field-effect transistors is usually silicon, a layer of silicon dioxide SiO2 grown on the surface of a silicon crystal by high-temperature oxidation is used as a dielectric. A metal electrode - a gate - is applied to the dielectric layer. The result is a structure consisting of a metal, a dielectric and a semiconductor. Therefore, field-effect transistors with an insulated gate are often called MOS transistors.

The input resistance of MOS transistors can reach 1010...1014 Ohms (for field-effect transistors with a control p-n junction 107...109), which is an advantage when building high-precision devices.

There are two types of MOS transistors: with an induced channel and with a built-in channel.

In induced-channel MOS transistors, there is no conductive channel between the heavily doped source and drain regions and, therefore, a noticeable drain current appears only at a certain polarity and at a certain value of the gate voltage relative to the source, which is called the threshold voltage (UTV).

In MOS transistors with a built-in channel, near the surface of the semiconductor under the gate, at zero voltage on the gate relative to the source, there is an inverse layer - a channel that connects the source to the drain.

Therefore, the heavily doped regions under the source and drain, as well as the induced and embedded channels, have p-type conductivity. If similar transistors are created on a substrate with p-type electrical conductivity, then their channel will have n-type electrical conductivity.

MOS transistors with induced channel

When the gate voltage relative to the source is zero, and when there is a voltage at the drain, the drain current turns out to be negligible. It represents the reverse current of the pn junction between the substrate and the heavily doped drain region. At a negative potential on the gate (for the structure shown in Fig. 2, a), as a result of the penetration of the electric field through the dielectric layer into the semiconductor at low voltages on the gate (smaller UGpores), a field effect layer and region depleted of the majority carriers appears at the surface of the semiconductor under the gate. space charge, consisting of ionized uncompensated impurity atoms. At gate voltages greater than UGpore, an inverse layer appears near the surface of the semiconductor under the gate, which is the channel connecting the source to the drain. The thickness and cross-section of the channel will change with changes in the gate voltage, and the drain current, that is, the current in the load circuit and a relatively powerful power source, will change accordingly. This is how the drain current is controlled in a field-effect transistor with an insulated gate and an induced channel.

Due to the fact that the gate is separated from the substrate by a dielectric layer, the current in the gate circuit is negligible, and the power consumed from the signal source in the gate circuit and required to control the relatively large drain current is also small. Thus, an induced-channel MOS transistor can produce amplification of electromagnetic oscillations in voltage and power.

The principle of power amplification in MOS transistors can be considered from the point of view of charge carriers transferring the energy of a constant electric field (the energy of the power source in the output circuit) to an alternating electric field. In an MOS transistor, before the channel appeared, almost all of the power supply voltage in the drain circuit dropped across the semiconductor between the source and drain, creating a relatively large constant component of the electric field strength. Under the influence of voltage on the gate, a channel appears in the semiconductor under the gate, along which charge carriers - holes - move from source to drain. The holes, moving in the direction of the constant component of the electric field, are accelerated by this field and their energy increases due to the energy of the power source in the drain circuit. Simultaneously with the emergence of the channel and the appearance of mobile charge carriers in it, the voltage at the drain decreases, that is, the instantaneous value of the variable component of the electric field in the channel is directed opposite to the constant component. Therefore, holes are inhibited by an alternating electric field, giving it part of their energy.

TIR structures for special purposes

In metal-nitride-oxide-semiconductor (MNOS) structures, the dielectric under the gate is made of two layers: a layer of SiO2 oxide and a thick layer of Si3N4 nitride. Electron traps are formed between the layers, which, when a positive voltage (28..30 V) is applied to the gate of the MNOS structure, capture electrons tunneling through a thin SiO2 layer. The resulting negatively charged ions increase the threshold voltage, and their charge can be stored for up to several years in the absence of power, since the SiO2 layer prevents charge leakage. When a large negative voltage (28...30 V) is applied to the gate, the accumulated charge is dissolved, which significantly reduces the threshold voltage.

Floating-gate avalanche injection metal-oxide-semiconductor (MOS) structures have a gate made of polycrystalline silicon that is isolated from other parts of the structure. Avalanche breakdown of the p-n junction of the substrate and the drain or source, to which a high voltage is applied, allows electrons to penetrate through the oxide layer to the gate, as a result of which a negative charge appears on it. The insulating properties of the dielectric allow this charge to be retained for decades. Removal of electrical charge from the gate is accomplished by ionizing ultraviolet irradiation with quartz lamps, while photocurrent allows electrons to recombine with holes.

Subsequently, double-gate memory field-effect transistor structures were developed. A gate built into the dielectric is used to store a charge that determines the state of the device, and an external (ordinary) gate, controlled by opposite-polarity pulses, is used to introduce or remove charge on the built-in (internal) gate. This is how cells and then flash memory chips appeared, which have become very popular these days and have become a significant competitor to hard drives in computers.

To implement very large-scale integrated circuits (VLSI), subminiature field-effect microtransistors were created. They are made using nanotechnology with a geometric resolution of less than 100 nm. In such devices, the thickness of the gate dielectric reaches several atomic layers. Various structures are used, including three-gate structures. The devices operate in micro-power mode. In modern Intel microprocessors, the number of devices ranges from tens of millions to 2 billion. The latest microfield-effect transistors are made on strained silicon, have a metal gate and use a new patented gate dielectric material based on hafnium compounds.

In the last quarter of a century, high-power field-effect transistors, mainly of the MIS type, have undergone rapid development. They consist of multiple low-power structures or structures with a branched gate configuration. Such HF and microwave devices were first created in the USSR by specialists from the Pulsar Research Institute V.V. Bachurin (silicon devices) and V. Ya. Vaxemburg (gallium arsenide devices). The study of their pulse properties was carried out by the scientific school of prof. Dyakonova V. P. (Smolensk branch of MPEI). This opened up the field of development of powerful switching (pulse) field-effect transistors with special structures having high operating voltages and currents (separately up to 500-1000 V and 50-100 A). Such devices are often controlled by low (up to 5 V) voltages, have low open resistance (up to 0.01 Ohm) for high-current devices, high transconductance and short (several to tens of ns) switching times. They do not have the phenomenon of accumulation of carriers in the structure and the phenomenon of saturation inherent in bipolar transistors. Thanks to this, high-power field-effect transistors are successfully replacing high-power bipolar transistors in the field of low- and medium-power power electronics.

Abroad, in recent decades, the technology of high-mobility electron transistors (HMETs) has been rapidly developing, which are widely used in microwave communication and radio surveillance devices. Based on TVPE, both hybrid and monolithic microwave integrated circuits are created. The operation of TVPE is based on channel control using a two-dimensional electron gas, the region of which is created under the gate contact due to the use of a heterojunction and a very thin dielectric layer - a spacer.

Application areas of field-effect transistors

A significant part of currently produced field-effect transistors are part of CMOS structures, which are built from field-effect transistors with channels of different (p- and n-) conductivity types and are widely used in digital and analog integrated circuits.

Due to the fact that field-effect transistors are controlled by the field (the voltage applied to the gate), and not by the current flowing through the base (as in bipolar transistors), field-effect transistors consume significantly less energy, which is especially important in circuits of waiting and tracking devices, as well as in low consumption and energy saving schemes (implementation of sleep modes).

Outstanding examples of devices based on field-effect transistors are quartz wristwatches and TV remote controls. Due to the use of CMOS structures, these devices can operate for up to several years because they consume virtually no energy.

The areas of application of high-power field-effect transistors are developing at a tremendous pace. Their use in radio transmitting devices makes it possible to obtain increased purity of the spectrum of emitted radio signals, reduce the level of interference and increase the reliability of radio transmitters. In power electronics, key high-power field-effect transistors are successfully replacing and displacing high-power bipolar transistors. In power converters, they make it possible to increase the conversion frequency by 1-2 orders of magnitude and sharply reduce the dimensions and weight of power converters. High power devices use field-controlled bipolar transistors (IGBTs) to successfully displace thyristors. In high-end HiFi and HiEnd audio power amplifiers, powerful field-effect transistors successfully replace powerful vacuum tubes with low nonlinear and dynamic distortions.

In addition to the main semiconductor material, usually used in the form of a single crystal, the transistor contains in its design alloying additives to the main material, lead metal, insulating elements, and housing parts (plastic or ceramic). Sometimes combined names are used that partially describe materials of a particular variety (for example, “silicon on sapphire” or “Metal-oxide-semiconductor”). However, the main ones are transistors:

Germanicaceae

Silicon

Gallium arsenide

Until recently, other transistor materials were not used. Currently, transistors based on, for example, transparent semiconductors are available for use in display matrices. A promising material for transistors is semiconductor polymers. There are also isolated reports of transistors based on carbon nanotubes.

Combined transistors

Resistor-equipped transistors (RETs) are bipolar transistors with resistors built into one housing.

Darlington transistor- a combination of two bipolar transistors, operating as a bipolar transistor with high current gain.

on transistors of the same polarity

on transistors of different polarities

A lambda diode is a two-terminal device, a combination of two field-effect transistors, which, like a tunnel diode, has a significant section with negative resistance.

An insulated gate bipolar transistor is a power electronic device designed primarily for controlling electric drives.

By power

Based on the power dissipated in the form of heat, they are distinguished:

low-power transistors up to 100 mW

medium power transistors from 0.1 to 1 W

powerful transistors (more than 1 W).

By execution

discrete transistors

case-based

For free installation

For installation on a radiator

For automated soldering systems

unframed

transistors in integrated circuits.

According to the material and design of the case

metal-glass

plastic

ceramic

Other types

Single-electron transistors contain a quantum dot (so-called “island”) between two tunnel junctions. The tunneling current is controlled by the voltage across the gate, which is capacitively coupled to it.

Biotransistor

Selection based on some characteristics

BISS (Breakthrough in Small Signal) transistors are bipolar transistors with improved small-signal parameters. A significant improvement in the parameters of BISS transistors was achieved by changing the design of the emitter zone. The first developments of this class of devices were also called “microcurrent devices”.

Transistors with built-in resistors RET (Resistor-equipped transistors) - bipolar transistors with resistors built into one housing. RET is a general purpose transistor with built-in one or two resistors. This design of the transistor makes it possible to reduce the number of attached components and minimize the required installation area. RET transistors are used to control the input signal of microcircuits or to switch smaller loads to LEDs.

The use of heterojunction allows the creation of high-speed and high-frequency field-effect transistors such as HEMT.

Application of transistors

Transistors are used as active (amplifying) elements in amplification and switching stages.

Relays and thyristors have a higher power gain than transistors, but operate only in switching mode.

The first known attempt to create a crystal amplifier in the United States was made by the German physicist Julius Lilienfeld, who patented it in 1930, 1932 and 1933. three amplifier options based on copper sulfide. In 1935, the German scientist Oskar Heil received a British patent for an amplifier based on vanadium pentoxide. In 1938, the German physicist Pohl created a working example of a crystal amplifier based on a heated potassium bromide crystal. In the pre-war years, several more similar patents were issued in Germany and England. These amplifiers can be considered the prototype of modern field-effect transistors. However, it was not possible to build stable operating devices, because at that time there were not enough pure materials and technologies for their processing. In the first half of the thirties, point triodes were made by two radio amateurs - Canadian Larry Kaiser and thirteen-year-old New Zealand schoolboy Robert Adams. In June 1948 (before the transistor was unveiled), the German physicists Robert Pohl and Rudolf Hilsch, who then lived in France, made their own version of a point-type germanium triode, which they called a transitron. At the beginning of 1949, the production of transitrons was organized; they were used in telephone equipment, and they worked better and longer than American transistors. In Russia in the 20s in Nizhny Novgorod, O.V. Losev observed a transistor effect in a system of three to four contacts on the surface of silicon and corborundum. In mid-1939, he wrote: “...with semiconductors a three-electrode system similar to a triode can be built,” but he was carried away by the LED effect he discovered and did not implement this idea. Many roads led to the transistor.

FIRST TRANSISTOR

The examples of transistor projects and samples described above were the results of local bursts of thought by talented or lucky people, which were not supported by sufficient economic and organizational support and did not play a serious role in the development of electronics. J. Bardeen, W. Brattain and W. Shockley found themselves in better conditions. They worked on the only purposeful long-term (more than 5 years) program in the world with sufficient financial and material support at Bell Telephone Laboratories, then one of the most powerful and knowledge-intensive in the USA. Their work began in the second half of the thirties, the work was headed by Joseph Becker, who attracted the highly qualified theorist W. Shockley and the brilliant experimenter W. Brattain to it. In 1939, Shockley put forward the idea of ​​changing the conductivity of a thin wafer of semiconductor (copper oxide) by applying an external electric field to it. It was something reminiscent of both the patent of Yu. Lilienfeld and the field-effect transistor that was later made and became widespread. In 1940, Shockley and Brattain made the fortunate decision to limit their research to the simple elements germanium and silicon. However, all attempts to build a solid-state amplifier came to nothing, and after Pearl Harbor (the practical beginning of World War II for the United States) they were shelved. Shockley and Brattain were sent to a research center working on radar. In 1945, both returned to Bell Labs. There, under Shockley's leadership, a strong team of physicists, chemists and engineers was created to work on solid-state devices. It included W. Brattain and theoretical physicist J. Bardeen. Shockley oriented the group towards the implementation of their pre-war idea. But the device stubbornly refused to work, and Shockley, having instructed Bardeen and Brattain to bring it to fruition, practically avoided the topic himself. Two years of hard work brought only negative results. Bardeen suggested that excess electrons were firmly deposited in the near-surface regions and screened the external field. This hypothesis prompted further actions. The flat control electrode was replaced with a tip, trying to locally influence the thin surface layer of the semiconductor.

One day, Brattain accidentally brought two needle-shaped electrodes on the surface of germanium almost closely together, and also mixed up the polarity of the supply voltages, and suddenly noticed the influence of the current of one electrode on the current of the other. Bardin immediately appreciated the mistake. And on December 16, 1947, they launched a solid-state amplifier, which is considered the world's first transistor. It was designed very simply - a germanium plate lay on a metal substrate-electrode, against which two closely spaced (10-15 microns) contacts rested. These contacts were originally made. A triangular plastic knife wrapped in gold foil, cut in half by a razor at the apex of the triangle. The triangle was pressed against the germanium plate with a special spring made from a curved paper clip. A week later, on December 23, 1947, the device was demonstrated to the management of the company, this day is considered the date of birth of the transistor. Everyone was happy with the result, except for Shockley: it turned out that he, who was the first to conceive a semiconductor amplifier, led a group of specialists, and lectured them on the quantum theory of semiconductors, did not participate in its creation. And the transistor didn’t turn out the way Shockley intended: bipolar, not field-effect. Therefore, he could not claim co-authorship in the “star” patent. The device worked, but this seemingly awkward design could not be shown to the general public. We made several transistors in the form of metal cylinders with a diameter of about 13 mm. and assembled a “tubeless” radio receiver on them. On June 30, 1948, the official presentation of a new device - a transistor (from the English Transver Resistor - resistance transformer) took place in New York. But experts did not immediately appreciate its capabilities. Experts from the Pentagon “sentenced” the transistor to use only in hearing aids for old people. So the myopia of the military saved the transistor from being classified. The presentation went almost unnoticed; only a couple of paragraphs about the transistor appeared in the New York Times on page 46 in the “Radio News” section. This was the appearance of one of the greatest discoveries of the 20th century to the world. Even manufacturers of vacuum tubes, who had invested many millions in their factories, did not see a threat in the appearance of the transistor. Later, in July 1948, information about this invention appeared in The Physical Review. But it was only after some time that experts realized that a grandiose event had occurred that determined the further development of progress in the world. Bell Labs immediately filed a patent for this revolutionary invention, but there were a lot of problems with the technology. The first transistors, which went on sale in 1948, did not inspire optimism - as soon as you shook them, the gain changed several times, and when heated, they stopped working altogether. But they had no equal in miniature size. Devices for people with reduced hearing could be placed in the frames of glasses! Realizing that it was unlikely to be able to cope with all the technological problems on its own, Bell Labs decided to take an unusual step. In early 1952, it announced that it would completely transfer the rights to manufacture the transistor to any company willing to pay the modest sum of $25,000 in lieu of regular patent fees, and it offered training courses in transistor technology, helping to spread the technology throughout the world. The importance of this miniature device gradually became clearer. The transistor turned out to be attractive for the following reasons: it was cheap, miniature, durable, consumed little power and turned on instantly (the lamps took a long time to heat up). In 1953, the first commercial transistorized product appeared on the market - a hearing aid (a pioneer in this business was John Kilby of Centralab, who a few years later would make the world's first semiconductor chip), and in October 1954, the first transistor radio, Regency TR1, it used only four germanium transistors. The computer technology industry immediately began to master new devices, the first being IBM. The availability of technology has borne fruit - the world began to change rapidly.

Inventors Stars: William Shockley, John Bardeen and Walter Brattain
A country: USA
Time of invention: 1948

The invention of the transistor in the late 1940s was one of the biggest milestones in the history of electronics. , which until then had been an indispensable and most important element of all radio and electronic devices for a long time, had many shortcomings.

As radio equipment became more complex and the general requirements for it increased, these shortcomings were felt more and more acutely. These include, first of all, the mechanical fragility of the lamps, their short service life, large dimensions, and low efficiency due to large heat losses at the anode.

Therefore, when vacuum tubes were replaced in the second half of the 20th century by semiconductor elements that did not have any of the listed flaws, a real revolution took place in radio engineering and electronics.

It must be said that semiconductors did not immediately reveal their remarkable properties to humans. For a long time, electrical engineering used exclusively conductors and dielectrics. A large group of materials that occupied an intermediate position between them did not find any application, and only a few researchers, studying the nature of electricity, from time to time showed interest in their electrical properties.

Thus, in 1874, Karl Ferdinand Braun discovered the phenomenon of current rectification at the point of contact between lead and pyrite and created the first crystal detector. Other researchers have found that the impurities they contain have a significant effect on the conductivity of semiconductors. For example, Boeddecker discovered in 1907 that the conductivity of copper iodide increases 24 times in the presence of an admixture of iodine, which itself is not a conductor.

What explains the properties of semiconductors and why have they become so important in electronics? Let's take a typical semiconductor like germanium. Under normal conditions, it has a resistivity 30 million times that of copper and 1,000,000 million times less than that of copper. Consequently, in its properties it is still somewhat closer to conductors than to dielectrics. As is known, the ability of a substance to conduct or not conduct electric current depends on the presence or absence of free charged particles in it.

Germany is no exception in this sense. Each of its atoms is tetravalent and must form with neighboring atoms have four electronic bonds. But due to thermal effects, some of the electrons leave their atoms and begin to move freely between the nodes of the crystal lattice. That's about 2 electrons for every 10 billion atoms.

One gram of germanium contains about 10 thousand billion atoms, that is, it has about 2 thousand billion free electrons. This is millions of times less than, for example, in copper or silver, but still enough for germanium to pass a small current through itself. However, as already mentioned, the conductivity of germanium can be significantly increased if impurities are introduced into its lattice, for example, a pentavalent atom of arsenic or antimony.

Then four electrons of arsenic form valence bonds with germanium atoms, but the fifth will remain free. It will be weakly bound to the atom, so small the voltage applied to the crystal will be enough for it to come off and turn into a free electron (it is clear that the arsenic atoms become positively charged ions). All this noticeably changes the electrical properties of germanium.

A different picture will occur when a trivalent impurity (for example, aluminum, gallium or indium) is introduced into a germanium crystal. Each impurity atom forms bonds with only three germanium atoms, and in place of the fourth bond there will be a free space - a hole that can easily be filled by any electron (in this case, the impurity atom is negatively ionized).

If this electron goes to an impurity from a neighboring germanium atom, then the hole will, in turn, be at the last one. By applying a voltage to such a crystal, we obtain an effect that can be called “movement of holes.” Indeed, let an electron fill the hole of a trivalent atom on the side where the negative pole of the external source is located. Consequently, the electron will move closer to the positive pole, while a new hole is created in the neighboring atom located closer to the negative pole.

Then the same phenomenon occurs with another atom. The new hole, in turn, will be filled with an electron, thus approaching the positive pole, and the resulting hole will approach the negative pole. And when, as a result of such movement, the electron reaches the positive pole, from where it goes to the current source, the hole will reach the negative pole, where it will be filled with an electron coming from the current source. The hole moves as if it were a particle with a positive charge, and we can say that here the electric current is created by positive charges. Such a semiconductor is called a p-type semiconductor (from positiv - positive).

In itself, the phenomenon of impurity conductivity is not yet of great importance, but when two semiconductors are connected - one with n-conductivity and the other with p-conductivity (for example, when n-conductivity is created in a germanium crystal on one side, and p on the other) -conductivity) - very interesting phenomena occur.

Negatively ionized atoms in region p will repel free electrons in region n from the transition, and positively ionized atoms in region n will repel holes in region p from the transition. That is, the pn junction will turn into a kind of barrier between the two areas. Thanks to this, the crystal will acquire pronounced one-way conductivity: for some currents it will behave as a conductor, and for others as an insulator.

In fact, if a voltage greater than the “stop” voltage of the p-n junction is applied to the crystal, and in such a way that the positive electrode is connected to the p-region, and the negative electrode to the n-region, then an electric current will flow in the crystal formed by electrons and holes moving towards each other.

If the potentials of the external source are changed in the opposite way, the current will stop (or rather, it will be very insignificant) - only the outflow of electrons and holes from the boundary between the two regions will occur, as a result of which the potential barrier between them will increase.

In this case, the semiconductor crystal will behave exactly like a vacuum tube diode, so devices based on this principle are called semiconductor diodes. Like tube diodes, they can serve as detectors, that is, current rectifiers.

An even more interesting phenomenon can be observed in the case when a semiconductor crystal is formed not one, but two p-n junctions. This semiconductor element is called a transistor. One of its outer regions is called the emitter, the other is called the collector, and the middle region (which is usually made very thin) is called the base.

If we apply voltage to the emitter and collector of a transistor, no current will flow, no matter how we change the polarity. But if you create a small potential difference between the emitter and the base, then free electrons from the emitter, having overcome the p-n junction, will enter the base. And since the base is very thin, only a small number of these electrons are enough to fill the holes located in the p region. Therefore, most of them will pass into the collector, overcoming the blocking barrier of the second junction - an electric current will arise in the transistor.

This phenomenon is all the more remarkable since the current in the emitter-base circuit is usually tens of times less than that flows in the emitter-collector circuit. From this it is clear that in its action the transistor can, in a certain sense, be considered an analogue of a three-electrode lamp (although the physical processes in them are completely different), and the base here plays the role of a grid placed between the anode and the cathode.

Just as in a lamp, a small change in the grid potential causes a large change in the plate current, in a transistor, small changes in the base circuit cause large changes in the collector current. Therefore, the transistor can be used as an amplifier and electrical signal generator.

Semiconductor elements began to gradually replace vacuum tubes from the early 40s. Since 1940, point germanium diodes have been widely used in radar devices. In general, radar served as a stimulus for the rapid development of electronics for powerful sources of high-frequency energy. Increasing interest was shown in decimeter and centimeter waves, in the creation of electronic devices capable of operating in these ranges.

Meanwhile, vacuum tubes, when used in the high and ultrahigh frequencies, behaved unsatisfactory, since their own noise significantly limited their sensitivity. The use of point germanium diodes at the inputs of radio receivers made it possible to sharply reduce their own noise and increase the sensitivity and detection range of objects.

However, the true era of semiconductors began after World War II, when the point-point transistor was invented.

It was created after many experiments in 1948 by employees of the American company Bell, William Shockley, John Bardeen and Walter Brattain. By placing two point contacts on a germanium crystal, at a short distance from each other, and applying a forward bias to one of them, and a reverse bias to the other, they were able to use the current passing through the first contact to control the current through the second. This first transistor had a gain of about 100.

The new invention quickly became widespread. The first point-point transistors consisted of a germanium crystal with n-conductivity, which served as a base on which two thin bronze tips rested, located very close to each other - at a distance of several microns.

One of them (usually beryllium) served as an emitter, and the other (phosphor bronze) served as a collector. When making the transistor, a current of approximately one ampere was passed through the tips. In this case, the germanium melted, as well as the tips of the points. Copper and the impurities present in it passed into germanium and formed layers with hole conductivity in the immediate vicinity of point contacts.

These transistors were not reliable due to the imperfection of their design. They were unstable and could not operate at high power. Their cost was great. However, they were much more reliable than vacuum tubes, were not afraid of dampness and consumed power hundreds of times less than similar vacuum tubes.

At the same time, they were extremely economical, since they required very little current to power them. about 0.5-1 V and did not require a separate battery. Their efficiency reached 70%, while that of the lamp rarely exceeded 10%. Since the transistors did not require heating, they began to work immediately after voltage was applied to them. In addition, they had a very low level of their own noise, and therefore equipment assembled with transistors turned out to be more sensitive.

Gradually the new device was improved. In 1952, the first planar germanium impurity transistors appeared. Their production was a complex technological process. First, germanium was purified from impurities, and then a single crystal was formed. An ordinary piece of germanium consists of a large number of crystals fused together in disorder. For semiconductor devices, this material structure is not suitable - here you need an exclusively correct crystal lattice, uniform for the entire piece. To do this, germanium was melted and a seed was dropped into it - a small crystal with a correctly oriented lattice.

By rotating the seed around its axis, it was slowly lifted. As a result, the atoms around the seed lined up into a regular crystal lattice. The semiconductor material solidified and enveloped the seed. The result was a monocrystalline rod. At the same time, a p or n type impurity was added to the melt. Then the single crystal was cut into small plates, which served as the base.

The emitter and collector were created in various ways. The simplest method was to place small pieces of indium on both sides of a germanium plate and quickly heat them to 600 degrees. In this case, indium was fused with the underlying germanium. Upon cooling, the indium-saturated regions acquired p-type conductivity. The crystal was then placed in the housing and the leads were connected.

In 1955, the Bell Systems company created a diffusion germanium transistor. The diffusion method consisted of placing semiconductor wafers in a gas atmosphere containing impurity vapors that would form the emitter and collector, and heating the wafers to a temperature close to the melting point. Impurity atoms gradually penetrated into the semiconductor.