Semiconductors occupy an intermediate place in electrical conductivity between conductors and non-conductors of electric current. The group of semiconductors includes many more substances than to groups of conductors and non-conductors taken together. Most characteristic representatives semiconductors who found practical application in technology are germanium, silicon, selenium, tellurium, arsenic, cuprous oxide and huge amount alloys and chemical compounds. Almost everything inorganic substances the world around us - semiconductors. The most common semiconductor in nature is silicon, which makes up about 30% of the earth's crust.
The qualitative difference between semiconductors and metals is manifested primarily in the dependence of resistivity on temperature. As the temperature decreases, the resistance of metals decreases. In semiconductors, on the contrary, as the temperature decreases, the resistance increases and near absolute zero they practically become insulators.
In semiconductors, the concentration of free charge carriers increases with increasing temperature. The mechanism of electric current in semiconductors cannot be explained within the gas model free electrons.
Germanium atoms have four weakly bound electrons in their outer shell. They are called valence electrons. In a crystal lattice, each atom is surrounded by four nearest neighbors. The bond between atoms in a germanium crystal is covalent, i.e., it occurs in pairs valence electrons. Each valence electron belongs to two atoms. The valence electrons in a germanium crystal are much more strongly bound to the atoms than in metals; Therefore, the concentration of conduction electrons at room temperature in semiconductors is many orders of magnitude lower than in metals. Near absolute zero temperature in a germanium crystal, all electrons are occupied in the formation of bonds. Such a crystal does not conduct electric current.
As the temperature increases, some of the valence electrons may gain enough energy to break covalent bonds. Then free electrons (conduction electrons) will appear in the crystal. At the same time, vacancies are formed in places where bonds are broken, which are not occupied by electrons. These vacancies are called “holes.”
At a given semiconductor temperature, a certain number of electron-hole pairs are formed per unit time. At the same time time goes by the reverse process - when a free electron meets a hole, the electronic bond between germanium atoms is restored. This process is called recombination. Electron-hole pairs can also be born when illuminating a semiconductor due to energy electromagnetic radiation.
If a semiconductor is placed in an electric field, then not only free electrons are involved in the ordered movement, but also holes, which behave like positively charged particles. Therefore, the current I in a semiconductor consists of the electron I n and hole I p currents: I = I n + I p.
The concentration of conduction electrons in a semiconductor is equal to the concentration of holes: n n = n p. The electron-hole conductivity mechanism manifests itself only in pure (i.e., without impurities) semiconductors. It is called the intrinsic electrical conductivity of semiconductors.
In the presence of impurities, the electrical conductivity of semiconductors changes greatly. For example, adding impurities phosphorus into crystal silicon in an amount of 0.001 atomic percent reduces resistivity by more than five orders of magnitude.
A semiconductor into which an impurity is introduced (i.e., part of atoms of one type is replaced by atoms of another type) is called impurity or doped.
There are two types of impurity conductivity - electronic and hole conductivity.
Thus, when doping a four-valence germanium (Ge) or silicon (Si) pentavalent - phosphorus (P), antimony (Sb), arsenic (As) An extra free electron appears at the location of the impurity atom. In this case, the impurity is called donor .
When doping four-valent germanium (Ge) or silicon (Si) with trivalent - aluminum (Al), indium (Jn), boron (B), gallium (Ga)
- a line hole appears. Such impurities are called acceptor
.
In the same sample semiconductor material one section may have p - conductivity, and the other n - conductivity. Such a device is called a semiconductor diode.
The prefix “di” in the word “diode” means “two”, it indicates that the device has two main “parts”, two semiconductor crystals closely adjacent to one another: one with p-conductivity (this is the zone p), the other - with n - conductivity (this is the zone p). In fact, a semiconductor diode is one crystal, into one part of which a donor impurity is introduced (zone p), to the other - acceptor (zone p).
If you connect the battery to a diode constant voltage"plus" to the zone r and “minus” to the zone n, then free charges - electrons and holes - will rush to the boundary and rush to the pn junction. Here they will neutralize each other, new charges will approach the boundary, and a D.C.. This is the so-called direct connection of a diode - charges move intensively through it, and a relatively large direct current flows in the circuit.
Now let’s change the polarity of the voltage on the diode and, as they say, turn it on in reverse - connect the “plus” battery to the zone p,"minus" - to the zone r. Free charges will be drawn away from the boundary, electrons will move to the “plus”, holes to the “minus” and as a result the pn junction will turn into a zone without free charges, into a clean insulator. This means that the circuit will break and the current in it will stop.
A small reverse current will still flow through the diode. Because, in addition to the main free charges (charge carriers) - electrons, in the zone n, and holes in the p zone - in each of the zones there is also an insignificant amount of charges of the opposite sign. These are their own minority charge carriers, they exist in any semiconductor, they appear in it due to the thermal movements of atoms, and it is they who create the reverse current through the diode. These charges are relatively small, and the reverse current is many times less than the forward current. The amount of reverse current strongly depends on: temperature environment, semiconductor material and area p-n transition. With an increase in the junction area, its volume increases, and therefore the number of minority carriers appearing as a result of thermal generation and thermal current increases. Often the current-voltage characteristics are presented in the form of graphs for clarity.
Physical properties semiconductors Semiconductors are materials that, in their own way, conductivity occupy an intermediate place between conductors and dielectrics. The main property of these materials is an increase in electrical conductivity with increasing temperature. Electrical properties substances Conductors Conduct electric current well These include metals, electrolytes, plasma... The most used conductors are Au, Ag, Cu, Al, Fe... Semiconductors Ranked by conductivity intermediate position between conductors and dielectrics Si, Ge, Se, In, As Dielectrics Practically do not conduct electric current These include plastics, rubber, glass, porcelain, dry wood, paper...
Physical properties of semiconductors The conductivity of semiconductors depends on temperature. Unlike conductors, whose resistance increases with temperature, the resistance of semiconductors decreases when heated. Near absolute zero, semiconductors have the properties of dielectrics. R (Ohm) metal R 0 semiconductor t (0 C)
Intrinsic conductivity of semiconductors Under normal conditions (low temperatures), there are no free charged particles in semiconductors, so the semiconductor does not conduct electric current. - Si Si - - Si
"Hole" When heated kinetic energy electrons increases and the fastest of them leave their orbit. When the bond between the electron and the nucleus is broken, a free space V electron shell atom. At this point a conditional positive charge, called a "hole". Si + Si - free electron Si - + - Si hole - + Si
Intrinsic conductivity of semiconductors The valence electron of a neighboring atom, being attracted to a hole, can jump into it (recombine). In this case, a new “hole” is formed in its original place, which can then similarly move around the crystal.
Intrinsic conductivity of semiconductors If the voltage electric field in the sample is zero, then the movement of the released electrons and “holes” occurs randomly and therefore does not create an electric current. Under the influence of an electric field, electrons and holes begin an ordered (counter) movement, forming an electric current. Conductivity under these conditions is called the intrinsic conductivity of semiconductors. In this case, the movement of electrons creates electronic conductivity, and the movement of holes creates hole conductivity.
Impurity conductivity of semiconductors Dosed introduction of impurities into a pure conductor allows you to purposefully change its conductivity. Therefore, to increase conductivity, impurities are introduced into pure semiconductors (doped), which are donor and acceptor impurities Acceptor Donor p-type semiconductors n-type semiconductors
Electronic semiconductors (n-type) come from B tetravalent semiconductor The term "n-type" (eg silicon) adds a pentavalent semiconductor impurity (eg arsenic). When doping 4-valence silicon (Si) with 5-valence arsenic (As), one of the 5 electrons of arsenic becomes free. IN in this case Charge transfer is carried out mainly by electrons, since their concentration is greater than that of holes. This conductivity is called electronic. Impurities that are added to semiconductors, causing them to become n-type semiconductors, are called donor impurities. The conductivity of N-semiconductors is approximately equal to: - Si Si - As - Si -
Hole semiconductors (p-type) The term “p-type” comes from the word “positive”, which denotes the positive charge of the majority carriers. Atoms of a trivalent element (such as indium) are added to a tetravalent semiconductor (such as silicon). The impurities that are added in this case are called acceptor impurities. If silicon is doped with trivalent indium, then indium lacks one electron to form bonds with silicon, i.e., an additional hole is formed. In such a semiconductor, the main charge carriers are holes, and the conductivity is called hole conductivity. The conductivity of P-semiconductors is approximately equal to: - Si Si - In + - Si
Direct connection p + + + n + + - - _ - The current through the p – n junction is carried out by the main charge carriers (holes, junction resistance is low, the current is high, moving to the right, electrons to the left)
Reverse switching p _ + + n + + - - + - Blocking layer Major charge carriers do not pass through the p – n junction. The junction resistance is high, the current is practically absent.
Diode A semiconductor diode is a semiconductor device with one electrical junction and two leads (electrodes). Unlike other types of diodes, the operating principle semiconductor diode is based on the phenomenon of p-n junction. The diode was first invented by John Flemming in 1904.
Types and applications of diodes Diodes are used in: conversion AC in constant detection of electrical signals protection different devices from incorrect polarity of switching on high-frequency signals, stabilization of current and voltage, transmission and reception of signals
Transistor electronic device made of semiconductor material, usually with three terminals, allowing input signals to control current in electrical circuit. Typically used to amplify, generate and convert electrical signals. In 1947, William Shockley, John Bardeen and Walter Brattain created the first working bipolar transistor at Bell Labs.
Bipolar transistor is a three-electrode semiconductor device, one of the types of transistor. 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. 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.
A field-effect transistor is a semiconductor device in which the current changes as a result of the action of an electric field perpendicular to the current created by the input signal. The flow of operating current in a field-effect transistor is caused by charge carriers of only one sign. A field-effect transistor is conventionally divided into 2 groups: with a control p-n junction or a metal-semiconductor junction with control via an insulated electrode (gate)
The word "current" means the movement or flow of something. Electric current is the ordered (directed) movement of charged particles. Typically, an electric current occurs when free charges are exposed to an external directed electromagnetic force. However, in semiconductors, the directed movement of charges is possible due to chaotic thermal movement if there is inhomogeneity in the density of their placement. In this case, charges preferentially move from an area with a higher concentration to an area with a lower concentration. This phenomenon is called diffusion, and the current due to diffusion is called diffusion.
To distinguish the ordinary current caused by the action electric force, from the diffusion current the ordinary current is called drift.
Electron-hole transition
When studying contact phenomena in semiconductors, one should focus on the methods of obtaining a transition: impurity melting, diffusion, ion implantation. All of them provide the creation of regions with electron and hole electrical conductivity in one semiconductor sample.
Even at the stage of creation of the transition, processes of diffusion of holes from the p-region to the n-region and free electrons from the n-region to the p-region occur in it. As a result, a double layer of electric charges is formed at the boundary of the two regions, consisting of negative and positive ions of impurity atoms, and an electric field generated by the transferred charges. This field counteracts further diffusion of the main charge carriers, due to which a state of equilibrium is established.
The region of the electron-hole transition is considered to be a layer of space charges on both sides of the boundary of the regions (Fig. 2.5). This layer is called a barrier layer because it is depleted of free charge carriers and in many cases can be considered a dielectric. Here it is necessary to emphasize that the space charge densities in the barrier layer are different on both sides of the boundary of the regions, since they are determined by the concentrations of the donor impurity in the n-region and the acceptor impurity in the p-region. In general, the double layer of space charge is electrically neutral: the total positive charge in the n-region is equal to the total negative charge in the p-region. The main effect of the electric field of a space charge is to weaken the diffusion current to a very small value of the conduction current (drift current) of the barrier layer. As a result, the total current through the junction turns out to be zero.
If an external voltage is applied to the junction, it adds to the contact voltage and, depending on the polarity, either increases or decreases the voltage at the junction, which leads to a change in the diffusion current through it. As for the drift current, its value is practically independent of the external voltage and is determined only by the generation rate of free carriers in the depletion layer. The one-way conductivity of the junction is due to the fact that with direct polarity of the external voltage, a very strong increase in the diffusion current is possible, and with reverse polarity, only a very slight decrease, since it was close to zero.
In addition, external stress has strong influence on the thickness of the barrier layer, the space charges of which are directly related to the voltage at the junction. An increase in this voltage should lead to an increase in space charges. However, the density of these charges is determined only by the concentrations of impurities. Consequently, an increase in charges will occur due to an increase in their volumes, which means an increase in the thickness of the barrier layer.
According to the specific value electrical resistance semiconductors occupy an intermediate position between good conductors and dielectrics. Semiconductors include many chemical elements(germanium, silicon, selenium, tellurium, arsenic, etc.), a huge number of alloys and chemical compounds. Almost all inorganic substances in the world around us are semiconductors. The most common semiconductor in nature is silicon, which makes up about 30% of the earth's crust.
The qualitative difference between semiconductors and metals is manifested primarily in the dependence of resistivity on temperature. As the temperature decreases, the resistance of metals decreases (see Fig. 1.12.4). In semiconductors, on the contrary, the resistance increases with decreasing temperature and near absolute zero they practically become insulators (Fig. 1.13.1).
Such a course of the dependence ρ ( T) shows that in semiconductors the concentration of free charge carriers does not remain constant, but increases with increasing temperature. The mechanism of electric current in semiconductors cannot be explained within the framework of the free electron gas model. Let us qualitatively consider this mechanism using the example of germanium (Ge). In a silicon (Si) crystal the mechanism is similar.
Germanium atoms have four weakly bound electrons in their outer shell. They are called valence electrons . In a crystal lattice, each atom is surrounded by its four nearest neighbors. The bond between atoms in a germanium crystal is covalent , i.e., it is carried out by pairs of valence electrons. Each valence electron belongs to two atoms (Fig. 1.13.2). Valence electrons in a germanium crystal are much more strongly bound to atoms than in metals; Therefore, the concentration of conduction electrons at room temperature in semiconductors is many orders of magnitude lower than in metals. Near absolute zero temperature in a germanium crystal, all electrons are occupied in the formation of bonds. Such a crystal does not conduct electric current.
As the temperature increases, some of the valence electrons may gain enough energy to break covalent bonds. Then free electrons (conduction electrons) will appear in the crystal. At the same time, vacancies are formed in places where bonds are broken, which are not occupied by electrons. These vacancies are called holes . The vacant place can be occupied by a valence electron from a neighboring pair, then the hole will move to a new place in the crystal. At a given semiconductor temperature, a certain number of electron-hole pairs are formed per unit time. At the same time, the reverse process occurs - when a free electron meets a hole, the electronic bond between the germanium atoms is restored. This process is called recombination . Electron-hole pairs can also be created when a semiconductor is illuminated due to the energy of electromagnetic radiation. In the absence of an electric field, conduction electrons and holes participate in chaotic thermal motion.
If a semiconductor is placed in an electric field, then not only free electrons are involved in the ordered movement, but also holes, which behave like positively charged particles. Therefore the current I in a semiconductor it consists of electron I n and hole Ip currents:
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The concentration of conduction electrons in a semiconductor is equal to the concentration of holes: n n = n p. The electron-hole conductivity mechanism manifests itself only in pure (i.e., without impurities) semiconductors. It's called own electrical conductivity semiconductors.
If there are impurities electrical conductivity semiconductors changes greatly. For example, adding phosphorus impurities in an amount of 0.001 atomic percent to a silicon crystal reduces the resistivity by more than five orders of magnitude. Such a strong influence of impurities can be explained on the basis of the above ideas about the structure of semiconductors.
A necessary condition for a sharp decrease in the resistivity of a semiconductor upon the introduction of impurities is the difference in the valence of the impurity atoms from the valence of the main atoms of the crystal.
The conductivity of semiconductors in the presence of impurities is called impurity conductivity . There are two types of impurity conductivity - electronic And hole.
Electronic conductivity occurs when pentavalent atoms (for example, arsenic atoms, As) are introduced into a germanium crystal with tetravalent atoms.
In Fig. 1.13.3 shows a pentavalent arsenic atom found in a node crystal lattice Germany. The four valence electrons of the arsenic atom are included in the formation of covalent bonds with four neighboring germanium atoms. The fifth valence electron turned out to be redundant; it easily breaks away from the arsenic atom and becomes free. An atom that has lost an electron becomes positive ion, located at a node of the crystal lattice. An impurity of atoms with a valency exceeding the valence of the main atoms of a semiconductor crystal is called donor impurity . As a result of its introduction, a significant number of free electrons appear in the crystal. This leads to a sharp decrease in the resistivity of the semiconductor - thousands and even millions of times. The resistivity of a conductor with a high content of impurities may approach that of a metal conductor.
In a germanium crystal with an admixture of arsenic, there are electrons and holes responsible for the crystal’s own conductivity. But the main type of free charge carriers are electrons detached from arsenic atoms. In such a crystal n n >> n p. This conductivity is called electronic, and a semiconductor having electronic conductivity, called n-type semiconductor .
Hole conductivity occurs when trivalent atoms (for example, indium atoms, In) are introduced into a germanium crystal. In Fig. Figure 1.13.4 shows an indium atom that, with the help of its valence electrons, has created covalent bonds with only three neighboring germanium atoms. The indium atom does not have an electron to form a bond with the fourth germanium atom. This missing electron can be captured by the indium atom from the covalent bond of neighboring germanium atoms. In this case, the indium atom turns into negative ion, located at a site of the crystal lattice, and a vacancy is formed in the covalent bond of neighboring atoms. An admixture of atoms capable of capturing electrons is called acceptor impurity . As a result of the introduction of an acceptor impurity, many covalent bonds are broken in the crystal and vacancies (holes) are formed. Electrons from neighboring covalent bonds can jump to these places, which leads to chaotic wandering of holes throughout the crystal.
The presence of an acceptor impurity sharply reduces the resistivity of the semiconductor due to the appearance large number free holes. The concentration of holes in a semiconductor with an acceptor impurity significantly exceeds the concentration of electrons that arose due to the mechanism of the semiconductor’s own electrical conductivity: n p >> n n. This type of conductivity is called hole conductivity. An impurity semiconductor with hole conductivity is called p-type semiconductor . The main free charge carriers in semiconductors p-type are holes.
It should be emphasized that hole conductivity is actually due to the relay movement of electrons through vacancies from one germanium atom to another, which carry out a covalent bond.
2. Problem on the topic "Motion of a body in a circle with a constant velocity modulus."
A ball on a string 80 cm long rotates around vertical axis With constant speed. If the angle of deviation of the thread from the vertical is 60°, then at what speed does the ball rotate?
3. Experimental task. Determination of the internal resistance of a galvanic cell.
Ticket No. 25-B
1. Nuclear reactions. Nuclear chain reactions. Nuclear reactor.
Nuclear reaction is a process of interaction atomic nucleus with another kernel or elementary particle, accompanied by a change in the composition and structure of the nucleus and the release large quantity energy. The nuclear reaction was first observed by Rutherford in 1919, bombarding the nuclei of nitrogen atoms with alpha particles; it was detected by the appearance of secondary ionizing particles with a range in the gas greater than the range of alpha particles and identified as protons. Subsequently, photographs of this process were obtained using a cloud chamber.
According to the mechanism of interaction, nuclear reactions are divided into two types:
· reactions with the formation of a compound nucleus are a two-stage process that occurs at a not very high kinetic energy of colliding particles (up to about 10 MeV).
direct nuclear reactions that take place during nuclear time required for the particle to cross the nucleus. This mechanism mainly manifests itself at high energies of bombarding particles.
Nuclear chain reaction- a sequence of single nuclear reactions, each of which is caused by a particle that appeared as a reaction product at the previous step of the sequence. An example of a chain nuclear reaction is chain reaction fission of nuclei of heavy elements, in which the main number of fission events is initiated by neutrons obtained during the fission of nuclei in the previous generation.
Nuclear reactor- this is a device designed to organize a controlled self-sustaining fission chain reaction, which is always accompanied by the release of energy (1 MW per 3·10 16 fission events per second). Otherwise: a nuclear reactor is a device that is designed to carry out a controlled nuclear reaction.
Any nuclear reactor consists of the following parts:
· Core with nuclear fuel and moderator;
· Neutron reflector surrounding the core;
· Coolant;
· Chain reaction control system, including emergency protection;
Current Status nuclear reactor can be characterized by the effective neutron multiplication factor k or reactivity ρ , which are related by the following relation:
These quantities are characterized following values:
· k> 1 - the chain reaction increases over time, the reactor is in supercritical state, its reactivity ρ > 0;
· k < 1 - реакция затухает, реактор - subcritical, ρ < 0;
· k = 1, ρ = 0 - the number of nuclear fissions is constant, the reactor is in a stable critical condition.
Criticality condition for a nuclear reactor:
· have a share full number neutrons generated in the reactor, absorbed in the reactor core, or the probability of avoiding neutron leakage from the final volume.
· k 0 - neutron multiplication factor in an infinitely large core.
Reversing the multiplication factor to unity is achieved by balancing the multiplication of neutrons with their losses. There are actually two reasons for the losses: capture without fission and leakage of neutrons outside the breeding medium.
2. Problem on the topic "Basic equation of the molecular kinetic theory of an ideal gas."
In a closed container there is ideal gas. If the root mean square speed of its molecules increases by 20%, then how will the gas pressure in the vessel change?
3. Experimental task. Checking the feasibility of the “golden rule of mechanics” for a lever.
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Ticket No. 26-B
1. Electromagnetic waves. Properties of electromagnetic waves. The speed of propagation of an electromagnetic wave.
Oscillatory movements of an electric charge also cause waves of changes in the electric and magnetic fields. Indeed, these charge fluctuations will first lead to periodic changes electric field around, which in turn, according to Maxwell's hypothesis (see §7), will cause the appearance of an alternating magnetic field of the same frequency. In this case, the resulting magnetic field will go beyond the oscillations of the electric charge that generated it. Then, the changing magnetic field according to the law electromagnetic induction will cause an electric shock greater distance from an oscillating charge, etc. Thus, the oscillatory movements of an electric charge lead to the appearance of waves of oscillations of the electric and magnetic fields propagating in space. Such waves are called electromagnetic.
The most important result, which follows from the theory formulated by Maxwell electromagnetic field, became a prediction of the possibility of the existence of electromagnetic waves. Electromagnetic wave- propagation of electromagnetic fields in space and time.
Electromagnetic field source - electric charges, moving with acceleration.
Electromagnetic waves, unlike elastic (sound) waves, can propagate in a vacuum or any other substance.
Electromagnetic waves in a vacuum propagate at speed c=299 792 km/s, that is, at the speed of light.
2. Problem on the topic "The law of the relationship between mass and energy."
The total radiation power of the Sun is 3.84 * 10 26 W. Determine how much the mass of the Sun decreases due to radiation per day.
3.Experimental task:
"Determination of the resultant of two forces directed along one straight line."
Eryutkin Evgeniy Sergeevich
higher physics teacher qualification category GOU secondary school No. 1360, Moscow
If you make a direct connection, then the external field will neutralize the blocking field, and the current will be carried by the main charge carriers.
Rice. 9. p-n junction with direct connection ()
In this case, the current of minority carriers is negligible, it is practically non-existent. Therefore, the p-n junction provides one-way conduction of electric current.
Rice. 10. Atomic structure of silicon with increasing temperature
The conductivity of semiconductors is electron-hole, and such conductivity is called intrinsic conductivity. And unlike conductor metals, as the temperature increases, the number of free charges increases (in the first case it does not change), therefore the conductivity of semiconductors increases with increasing temperature, and the resistance decreases
Very important issue in the study of semiconductors is the presence of impurities in them. And in the case of the presence of impurities, we should already talk about impurity conductivity.
Small size and very high quality of transmitted signals have made semiconductor devices very common in modern electronic technology. The composition of such devices may include not only the aforementioned silicon with impurities, but also, for example, germanium.
One such device is a diode - a device that can pass current in one direction and prevent it from passing in another. It is obtained by implanting a semiconductor of another type into a p- or n-type semiconductor crystal.
Rice. 11. Designation of the diode on the diagram and the diagram of its device, respectively
Another device, now with two p-n junctions called a transistor. It serves not only to select the direction of current transmission, but also to transform it.
Rice. 12. Diagram of the structure of the transistor and its designation on electrical diagram respectively ()
It should be noted that modern microcircuits use many combinations of diodes, transistors and other electrical devices.
In the next lesson we will look at the propagation of electric current in a vacuum.
- Tikhomirova S.A., Yavorsky B.M. Physics ( basic level) M.: Mnemosyne. 2012
- Gendenshtein L.E., Dick Yu.I. Physics 10th grade. M.: Ilexa. 2005
- Myakishev G.Ya., Sinyakov A.Z., Slobodskov B.A. Physics. Electrodynamics M.: 2010
- Principles of operation of devices ().
- Encyclopedia of Physics and Technology ().
- What causes conduction electrons to appear in a semiconductor?
- What's happened intrinsic conductivity semiconductor?
- How does the conductivity of a semiconductor depend on temperature?
- How does a donor impurity differ from an acceptor impurity?
- *What is the conductivity of silicon with an admixture of a) gallium, b) indium, c) phosphorus, d) antimony?
