Home Windows 10 Development of a physics lesson on the topic “electric current in semiconductors.” Lecture notes "Semiconductors" Lesson plan on the topic of semiconductor materials

Development of a physics lesson on the topic “electric current in semiconductors.” Lecture notes "Semiconductors" Lesson plan on the topic of semiconductor materials

Topic: Semiconductors.

Purpose and objectives of the lesson:

· Educational: to form in the minds of students initial concepts about the electrical properties of semiconductors.

· Educational: continue to foster a culture of mental work, the development of personal qualities - perseverance, determination, creative activity, independence.

· Developmental: expand students’ scientific worldview to the phenomena they observe every day.

Equipment and visual aids:

Power supply, semiconductor diodes, light bulbs, connecting wires, demonstration stand, electrical measuring instrument - tester, information posters.

Lesson progress:

1. Organizational moment: (Task: creating a favorable psychological mood and activating attention).

2. Preparation for repetition and generalization of the material covered:

Graphic symbols of radioelements.

What's happened electric current?

Current strength, units of measurement.

The class is divided into teams and a competition is held to see who can draw the most symbols of radio elements and explain their purpose.

State the topic and purpose of the lesson.

Semiconductors. We must form initial concepts about the electrical properties of semiconductors.

Explanation of perspective.

Semiconductors in the form of various electronic devices are present in all aspects of our lives. Who can name specific applications of semiconductors?

(Possible answers: LED traffic lights, laser pointer, computers, televisions, cameras, television cameras, intercoms, washing machines, etc.)

We can say that the study and use of semiconductors has a significant impact on the content and quality of our lives. Let's consider in order what semiconductors are, what properties they have, what semiconductor devices have been created based on them, and what interesting experiments can be carried out with them.

3. Main stage.

New material

All substances found in nature are divided into three groups according to their electrical conductive properties:

Ш Conductors,

Ш insulators (dielectrics),

Ш semiconductors

frontal poll:

Question: “Why do metals conduct electric current well, but dielectrics practically do not?”

Answer: "in the conductors there is large number free electrons, but dielectrics do not have them.

Question: “Are there no electrons in dielectrics?”

Answer: “There are no fewer electrons there than in metals, but they are bound to atoms and cannot move throughout the volume of the sample.”

Right.

The question of the electrical conductivity of a material is a question of the presence of free, i.e., elements in it. electrical charges capable of moving. According to this indicator, semiconductors occupy an intermediate position between conductors and dielectrics.

Semiconductors include elements of group 4 of the periodic table, as well as some chemical compounds. A particularly convenient material to use is silicon (Si). The valence electrons of a semiconductor, like a dielectric, are connected to their atoms, but this connection is not as strong as in dielectrics. At room temperature, the thermal vibration energy is sufficient to cause some of the valence electrons to break away from their atoms and become free within the semiconductor sample. As a result, the semiconductor sample acquires the so-called electronic conductivity.

The departure of some valence electrons from their atoms gives rise to the second mechanism of electrical conductivity in semiconductors, which is called hole electrical conductivity. The fact is that the valence electron of a neighboring atom can move to the vacant place of the vacated electron. As a result, a vacancy, called a hole, can move throughout the volume of the sample and transfer electric charge. In fact, the movement and relay charge transfer are carried out by valence electrons, but the introduction of an imaginary particle with an elementary positive charge - a hole - turned out to be very convenient and has become firmly established in semiconductor physics.

Free electrons leaving their atoms create n-conductivity (n is the first letter of the Latin word negativus - negative). Holes create p - conductivity in a semiconductor (p is the first letter of the Latin word positivus - positive). - given for recording.

In a pure semiconductor, the number of free electrons and holes is the same.

By adding impurities, it is possible to obtain a semiconductor with predominantly electron or hole conductivity.

If we add 5-valence arsenic (antimony) to a 4-valence silicon crystal, we get an n - conductor.

By adding 3-valent indium, we get p - conductor.

A tiny amount of impurity is enough to change the concentration of free electrons or holes by several orders of magnitude. Therefore, free charge carriers formed due to impurities are called major, and the semiconductor's own free charge carriers are called minority.

Contact between electron and hole semiconductors (p-n junction).

If you simply bring two separate semiconductor samples with p and n conductivity into contact, then no current will flow through this connection. Semiconductor samples in air are covered with an oxide film, which is an excellent dielectric. The contact between electron and hole semiconductors is created within a single sample. To do this, for example, a semiconductor with hole electrical conductivity on one of the surfaces is doped with a donor impurity. As a result, the type of electrical conductivity at the surface becomes electronic, while hole conductivity remains in the depths. Consequently, a p-n junction appears, schematically shown in the figure.

The thermal movement of holes in the p-region and free electrons in the n-region will lead to their preferential movement from areas of high concentration to areas of lower concentrations. This process is called diffusion (under writing). As a result, holes from the p-region will rush to the n-region, and free electrons will flow from the n-region to the p. Those. A directed movement of charged particles occurs, which is an electric current. Since this current is due to diffusion, it is called diffusion current. In this case, the electrons transferred to the p-region turn out to be captured by atoms of the acceptor impurity, and the holes transferred to the n-region are nothing more than valence electrons of the donor impurity

The side of the p-region adjacent to the transition boundary is charged negatively, and the side of the n-region is charged positively. All these processes occur during the creation of the transition. As a result, the so-called transition occurs at the transition. contact potential difference, which acts against the diffusion current and reduces it to almost zero.

Electron-hole transition in an electrical circuit.

Let's perform the following experiment: Let's connect the electron-hole junction in series to a simple circuit, which consists of a source of constant EMF and a light bulb.

When the positive terminal of the EMF source is connected to the p-region, and the negative terminal through the light bulb is connected to n, a strong current flows in the circuit, which is indicated by the glow of the light bulb. When the transition is switched on in reverse polarity, there is no current in the circuit. This experiment suggests that the junction has one-way conductivity. Let us determine the mechanism of this effect.

In the first case, when the positive pole of the source is connected to the p-region, and the minus pole to the n-region, the voltage external source opposite in polarity to contact voltage. Consequently, the total voltage at the junction decreases in comparison with the equilibrium state. The opposition of this voltage to the diffusion current decreases, and this current increases greatly.

In the second case, the external voltage coincides in polarity with the contact voltage. In this case, the total voltage increases, which leads to a weakening of the diffusion current. Since this current has already been weakened almost to zero by the contact voltage, it remains practically zero.

Thus, the one-way conductivity of the p-n junction is due to the unidirectionality of the diffusion current through the junction. As for the drift current, it is always close to zero, since it is determined by very low concentrations of minority carriers in the p and n regions.

The polarity of the external voltage at the junction, at which it passes current, and the current itself in this case are called forward, the opposite polarity of the voltage and current are called reverse.

The one-way conductivity of the pn junction is reflected in its symbols. In all cases, a contact is depicted and an arrow showing the direction of current flow - from the p-region to n (under the notation).

Fixing the material. Frontal survey.

1. What materials are classified as semiconductors?

2. Explain the mechanism of intrinsic electrical conductivity of semiconductors?

3. How does an impurity increase the electrical conductivity of a semiconductor.

4. Explain the mechanism of formation of electronic impurity electrical conductivity.

5. Explain the mechanism of formation of hole impurity electrical conductivity.

6. What is a p-n junction, how is it made,

7. Explain the one-way conductivity of a p-n junction.

Homework: review the material covered. Think about solving the following problem:

The chandelier has two light bulbs. Typically, to turn them on and off independently, three wires are used running from the switches to the chandelier. Is it possible, using the one-way electrical conductivity of p-n junctions, to get by with only two wires if you assemble the circuit shown in the figure.

(Answer: Yes you can, switch A controls light bulb a, switch B controls light bulb b)

Demonstration of changes in semiconductor resistance when illuminated

The installation is assembled with a photoresistor according to the drawing. Close the key and note the galvanometer reading (2-4 divisions). Turn on an electric lamp located at a distance of 0.5 m from the photoresistor, and slowly bring it closer to the photoresistor, monitoring the reading of the galvanometer. Students are reminded that when illuminated, conductivity increases, which means resistance decreases.

LESSON 10/10

Subject. Electric current in semiconductors

Objective of the lesson: to form an idea of free media electric charge in semiconductors and the nature of electric current in semiconductors.

Lesson type: lesson on learning new material.

LESSON PLAN

Knowledge control		1. Electric current in metals. 2. Electric current in electrolytes. 3. Faraday's law for electrolysis. 4. Electric current in gases
Demonstrations		Fragments of the video “Electric current in semiconductors”
Learning new material		1. Charge carriers in semiconductors. 2. Impurity conductivity of semiconductors. 3. Electron-hole transition. 4. Semiconductor diodes and transistors. 5. Integrated circuits
Reinforcing the material learned		1. Qualitative questions. 2. Learning to solve problems

LEARNING NEW MATERIAL

The resistivities of semiconductors at room temperature have values that are in a wide range, i.e., from 10-3 to 107 Ohm m, and occupy an intermediate position between metals and dielectrics.

Ø Semiconductors are substances whose resistivity decreases very quickly with increasing temperature.

Semiconductors include many chemical elements (boron, silicon, germanium, phosphorus, arsenic, selenium, tellurium, etc.), huge amount minerals, alloys and chemical compounds. Almost all inorganic substances in the world around us are semiconductors.

For sufficiently low temperatures and absence external influences(eg lighting or heating) semiconductors do not conduct electricity: under these conditions, all electrons in semiconductors are bound.

However, the bond between electrons and their atoms in semiconductors is not as strong as in dielectrics. And in the case of an increase in temperature, as well as in bright lighting, some electrons are detached from their atoms and become free charges, that is, they can move throughout the sample.

Due to this, negative charge carriers - free electrons - appear in semiconductors.

Ø The conductivity of a semiconductor due to the movement of electrons is called electronic.

When an electron is removed from an atom, the positive charge of that atom becomes uncompensated, that is, an extra positive charge appears in that place. This positive charge is called a "hole". An atom near which a hole has formed can take away a bound electron from a neighboring atom, while the hole will move to the neighboring atom, and the atom, in turn, can “transfer” the hole further.

This “relay” movement of bound electrons can be considered as the movement of holes, that is, positive charges.

Ø The conductivity of a semiconductor due to the movement of holes is called hole conductivity.

Thus, the difference between hole conductivity and electronic conductivity lies in the fact that electronic conductivity is due to the movement of free electrons in semiconductors, and hole conductivity is due to the movement of bound electrons.

Ø In a pure semiconductor (without impurities), an electric current creates the same number of free electrons and holes. This conductivity is called the intrinsic conductivity of semiconductors.

If you add a small amount of arsenic (about 10-5%) to pure molten silicon, after hardening a regular silicon crystal lattice is formed, but in some lattice sites there will be arsenic atoms instead of silicon atoms.

Arsenic is known to be a pentavalent element. Chotrivalent electrons form paired electrons electronic communications with neighboring silicon atoms. The fifth valence electron will not have enough bonding, and it will be weakly bound to the Arsenic atom, which easily becomes free. As a result, each impurity atom will give one free electron.

Ø Impurities whose atoms easily give up electrons are called donors.

Electrons from silicon atoms can become free, forming a hole, so both free electrons and holes can exist in the crystal at the same time. However, there will be many times more free electrons than holes.

Semiconductors in which the main charge carriers are electrons are called n-type semiconductors.

If a small amount of trivalent indium is added to silicon, the nature of the conductivity of the semiconductor will change. Since indium has three valence electrons, it can form covalent bonds with only three neighboring atoms. There is not enough electron to establish a bond with the fourth atom. Indium “borrows” an electron from neighboring atoms, as a result, each Indian atom forms one vacant site - a hole.

Ø Impurities that “capture” electrons from the atoms of the crystal lattice of semiconductors are called acceptor impurities.

In the case of an acceptor impurity, the main charge carriers when an electric current passes through the semiconductor are holes. Semiconductors in which the main charge carriers are holes are called p-type semiconductors.

Almost all semiconductors contain both donor and acceptor impurities. The conductivity type of a semiconductor is determined by an impurity with a higher concentration of charge carriers - electrons and holes.

Consequently, across the interface between n-type and p-type semiconductors, electric current flows in only one direction - from the p-type semiconductor to the n-type semiconductor.

This is used in devices called diodes.

Semiconductor diodes are used to rectify alternating current (this current is called alternating current), as well as for the manufacture of LEDs. Semiconductor rectifiers have high reliability and a long service life.

Semiconductor diodes are widely used in radio engineering devices: radios, VCRs, televisions, computers.

An even more important application of semiconductors was the transistor. It consists of three layers of semiconductors: along the edges there are semiconductors of one type, and between them there is a thin layer of another type of semiconductor. The widespread use of transistors is due to the fact that they can be used to amplify electrical signals. Therefore, the transistor has become the main element of many semiconductor devices.

Semiconductor diodes and transistors are the building blocks of very complex devices called integrated circuits.

Microcircuits “work” today in computers and televisions, in mobile phones And artificial satellites, in cars, airplanes and even in washing machines. An integrated circuit is made on a wafer of silicon. The size of the plate is from a millimeter to a centimeter, and one such plate can accommodate up to a million components - tiny diodes, transistors, resistors, etc.

Important advantages of integrated circuits are high speed and reliability, as well as low cost. It is thanks to this that, based on integrated circuits, it was possible to create complex, but accessible to many devices, computers and modern household appliances.

QUESTIONS FOR STUDENTS DURING PRESENTATION OF NEW MATERIAL

First level

1. What substances can be classified as semiconductors?

2. The movement of which charged particles creates a current in semiconductors?

3. Why does the resistance of semiconductors depend so much on the presence of impurities?

4. How is a p-n junction formed? What property does a p-n junction have?

5. Why can’t free charge carriers pass through the p-n junction of a semiconductor?

Second level

1. After introducing arsenic impurities into germanium, the concentration of conduction electrons increased. How did the concentration of holes change?

2. Using what experience can you verify the one-way conductivity of a semiconductor diode?

3. Is it possible to obtain a p-n junction by fusing tin into germanium or silicon?

CONSTRUCTION OF LEARNED MATERIAL

1. What kind of conductivity (electronic or hole) does silicon doped with gallium have? India? phosphorus? antimony?

2. What kind of conductivity (electronic or hole) will silicon have if phosphorus is added to it? boron? aluminum? arsenic?

3. How will the resistance of a silicon sample with an admixture of phosphorus change if a gallium admixture is introduced into it? The concentration of Phosphorus and Gallium atoms is the same. (Answer: will increase)

WHAT WE LEARNED IN LESSON

· Semiconductors are substances whose resistivity decreases very quickly with increasing temperature.

· The conductivity of a semiconductor due to the movement of electrons is called electronic.

· The conductivity of a semiconductor due to the movement of holes is called hole conductivity.

· Impurities whose atoms easily give up electrons are called donors.

· Semiconductors in which the main charge carriers are electrons are called n-type semiconductors.

· Impurities that “capture” electrons from the atoms of the crystal lattice of semiconductors are called acceptor impurities.

· Semiconductors in which the main charge carriers are holes are called p-type semiconductors.

Contact of two semiconductors with various types conductivity has the properties of conducting current well in one direction and much worse in the opposite direction, that is, it has one-way conductivity.

Riv1 No. 6.5; 6.7; 6.15; 6.17.

Riv2 No. 6.16; 6.18; 6.24, 6.25.

Riv3 No. 6.26, 6.28; 6.29; 6.30.

3. D: prepare for independent work No. 4.

An auction using key words as a methodological technique for updating basic knowledge, the use of ICT, game moments that allow you to change the types of activities in the lesson, individual work when consolidating the studied material and subsequent mutual verification of completed tasks - all these are elements that make an ordinary lesson a little more interesting.

Physics lesson development

Lesson topic: Electric current in semiconductors.

Lesson objectives:

Didactic - Introduce students to a special class of substances - semiconductors, introduce the concepts of intrinsic and impurity conductivity, study the dependence of the electrical conductivity of semiconductors on temperature and the presence of impurities.

Developmental: To help broaden the horizons of students, develop the ability to perceive and analyze technical and scientific information, and the ability to use technical terminology.

Educational: Develop a responsible attitude towards acquiring knowledge, communication skills and self-discipline.

MTO lesson: media equipment, presentation “Electric current in semiconductors”, containing an animated explanation of the material being studied, cards with keywords, handout didactic material for independent work.

Interdisciplinary connections. Chemistry. Topics: Periodic table of chemical elements by D.I. Mendeleev. Covalent bond.

Lesson type: A lesson in learning new knowledge based on existing knowledge.

Methods and techniques: auction using reference words, use of ICT, use of game moments to create health-saving conditions, frontal survey, individual work, mutual verification.

Lesson Plan.

1. Organizational moment.

2. Updating basic knowledge.

3. Studying new material.

3.1. Semiconductors.

3.2. Intrinsic conductivity of semiconductors;

3.3. Impurity conductivity;

3.3.1. Donor impurities;

3.3.2. Acceptor impurities.

4. Consolidation of the studied material.

5. Homework.

6. Summing up the lesson. Evaluation of student work.

Progress of the lesson.

1. Organizational moment.

2. Updating basic knowledge(survey in the form of an auction using cards with keywords).

Auction methodology .

The teacher shows a card with keywords (words), and students speak in accordance with the given topic, without going into detail. Each correct answer is a point for the student (the card remains with him temporarily to calculate points in the future).

Card. Electric current

Answer. Electric current is the ordered directional movement of free charged particles.

Card. Constant electric current.

Answer. An electric current that does not change either in magnitude or direction is called direct current.

Card. Direction of direct current.

Answer. The direction of movement of positively charged particles is taken as the direction of direct current, i.e. from “+” to “-”.

Card. Conditions for the existence of current

Answer. For the existence of an electric current, it is necessary to have free charged particles and forces that would cause these particles to move in a direction. For example, electric field strength.

Card. Groups of substances based on electrical conductivity.

Answer. Based on electrical conductivity, substances are divided into conductors and dielectrics.

Card. Conductors.

Answer. Conductors are substances that conduct current well.

Card. Dielectrics

Answer. Dielectrics are substances that do not conduct current.

3. Learning new material accompanied by a presentation.

- Write down the topic of the lesson in your notebook(slide 1).

Motivation for further study of the topic (slide 2).

Let's get acquainted with the goals of this lesson (slide 3).

We correct our ideas about groups of substances based on electrical conductivity (slide 4).

Write it down in a notebook

Based on electrical conductivity, substances can be divided into 3 main groups: conductors, dielectrics, and semiconductors.

Conductors that conduct electric current well (metals, electrolyte solutions, plasma, etc.) The most used conductors are Au, Ag, Cu, Al, Fe.

Dielectrics are substances that practically do not conduct electric current (plastics, rubber, glass, porcelain, dry wood, paper, etc.)

3.1. Semiconductors

We write it down in a notebook.

Semiconductors are substances that conduct current only under certain conditions.

Their electrical conductivity depends on temperature, illumination, and the presence of impurities(Si, Ge, Se, In, Asetc.).

In terms of electrical conductivity, they occupy an intermediate position between conductors and dielectrics (Si, Ge, Se, In, As, etc.) In addition to 12 pure chemical elements, semiconductors are lead sulfide, cadmium sulfide, cuprous oxide, many metal oxides and sulfides, some organic substances. The most widely used in technology are germanium Ge and silicon Si (slides 4,5,6).

Just over half a century ago, semiconductors had no significant practical significance. In electrical engineering and radio engineering they used exclusively conductors and dielectrics. But the situation changed dramatically when, theoretically and then practically, the possibility of controlling the electrical conductivity of semiconductors was discovered.

What is the main difference between semiconductors and conductors, and what features of their structure have made it possible to widely use semiconductor devices in almost all electronic devices?

3.2. Self conductivity

We write it down in a notebook.

The conductivity of pure semiconductors is called own conductivity .

Let us once again recall the conditions for the existence of current. We repeat the mechanism of electrical conductivity of metals, focusing on the role of the electric field (slide 8).

Student response

For the existence of an electric current, it is necessary to have free charged particles and forces that would cause these particles to move in a direction. These may be the forces of an electric field, which causes electrons to move in an orderly manner.

Let's consider the conductivity of semiconductors using the example of silicon Si (slide 9).

Silicon is a tetravalent chemical element. Each silicon atom in the outer electron layer has four unpaired electrons, which form electron pairs (covalent bonds) with four neighboring atoms. Thus, in a semiconductor there are no free charged particles capable of creating a current.

But this happens under normal conditions, at low temperatures.

- What happens if you increase the temperature of a substance (slide 10)?

As the temperature increases, the energy and speed of electrons increase and some of them break away from their atoms, becoming free electrons. The remaining vacant places with an uncompensated positive charge ( virtual charged particles), are called holes. Under the influence of an electric field, electrons and holes begin an ordered (counter) movement, forming an electric current.

To understand how holes (vacant space) move, play the game “Empty Chair”.

Method of playing the game .

The essence of the game is as follows. We vacate a chair in one of the rows at the first desk. This is the starting position. The student sitting at the second desk moves to it. Thus, the free chair is no longer at the first, but at the second desk. Now the student sitting at the third desk takes the vacant seat, and the chair at the third desk is empty, etc. Thus, a vacant place - an empty chair (in a semiconductor this is a hole) moves further and further from the first desk, moving in the direction opposite to the movement of the participants in the game (in a semiconductor - in the direction opposite to the movement of electrons).

The game helps relieve stress and continue further successful learning of the educational material.

We write it down in a notebook.

Electric current in pure semiconductors is created by free electrons and holes, of which there are equal numbers.

This is the intrinsic conductivity of semiconductors.

As the temperature increases, the number of free electrons and holes increases, the conductivity of semiconductors increases, and the resistance decreases.

We write it down in a notebook.

As the temperature increases, the conductivity of semiconductors increases and the resistance decreases.

Assignment for students.

Compare and explain graphs of the resistance of metals and semiconductors versus temperature (slide 11).

Students' answers on the slide.

As the temperature increases, the resistance of metals increases. This is explained by the fact that with increasing temperature, the ions at the nodes of the crystal lattice vibrate more intensely, the randomness of the movement of free electrons increases, and the total charge passing through the cross section of the conductor per unit time decreases.

As temperature increases, the resistance of semiconductors decreases. This is explained by the fact that when semiconductors are heated, there are more free charge carriers in them, which leads to an increase in current strength, and this is equivalent to a decrease in resistance.

3.3 Impurity conductivity of semiconductors(slides 12,13,14).

The intrinsic conductivity of semiconductors is clearly insufficient for the technical application of semiconductors. Therefore, to increase conductivity, impurities are introduced into pure semiconductors (doped), which can be donor And acceptor

Write it down in a notebook

The conductivity of semiconductors with added impurities is called impurity conductivity. Impuritiesthere are donor and acceptor

3.3.1. Donorimpurities.

Arsenic is known to be a pentavalent element. The tetravalent electrons form paired electronic bonds with neighboring silicon atoms. The fifth valence electron will not have enough bonding, and it will be weakly bound to the Arsenic atom, which easily becomes free. As a result, each impurity atom will give up one free electron.

Semiconductors in which the main charge carriers are electrons are called n-type semiconductors.

Write it down in a notebook

Impurities whose atoms easily give up electrons are called donor impurities (semiconductorn-type).

3.3.2. Acceptor impurities

In the case of an acceptor impurity, the main charge carriers during the passage of electric current through the semiconductor are holes. Semiconductors in which the main charge carriers are holes are called p-type semiconductors.

Write it down in a notebook

Impurities that “capture” electrons from the atoms of the crystal lattice of semiconductors are called acceptor impurities (p-type semiconductor).

4. Consolidation studied material.

4.1. Frontal survey(slide 16).

What are semiconductors?

What particles create current in semiconductors?

How does impurity conductivity differ from intrinsic conductivity?

Why are pure semiconductors doped?

What is a semiconductor r- like?

What is a semiconductor n- like?

Why does the resistance of semiconductors decrease with increasing temperature?

4.2. Independent work using cards.

Match what physical terms and statements are necessary for a story on the topics “Electric current in metals”, “Electric current in gases”, “Electric current in electrolyte solutions”, “Electric current in semiconductors”?

Condition: corrections are not allowed while performing the work .

Metals Gases Electrolyte solutions Semiconductors

1. Ions, 2. Electrons, 3. Impurities, 4. Hole, 5. Resistance increases with temperature, 6. Recombination, 7. Resistance decreases when heated, 8. Conductor, 9. Crystal lattice, 10. Electric arc, 11 .Self-discharge,12. St. Elmo's Fire, 13. Donor, 14. Dielectric, 15. Electron cloud, 16. Vacuum diode, 17. Gas discharge tube, 18. Acceptor, 19. Intrinsic conductivity, 20. Vacuum, 21. Superconductivity, 22. Ionization, 23. Electrolytic dissociation, 24. Electrodes, 25. Electrolysis, 26. Kinescope, 27. Electroplating.

After completing the task, students exchange cards and check each other, making corrections, evaluating the work of a friend.

Then the work is checked again using the key and transferred to the teacher.

Key to the task

Metals – 1, 2, 5, 8, 9, 21.

Gases – 1,2,6,7,10,11,12,14,17,22.

Electrolyte solutions – 1,6,7,23,24,25,27.

Semiconductors – 1,2,3,4,7,9,13,18,19.

5. Homework:

1. Prepare a comparative table “Electric current in various environments.”

2. Prepare the message “First practical application semiconductor thermoelements during the Second World War" ("Partisan Cauldron") - optional.

6. Summing up. Evaluation of student work.

Literature used

Physics: Textbook. for 10th grade general education institutions/ G.Ya. Myakishev, B.B. Bukhovtsev, N.N. Sotsky - 12th ed. - M. : Education, 2010. - 336 pp.,: ill.-ISBN 5-01 011578-8.

Electronic textbook “Open Physics”, Physikon

Labor training lesson plan.

Class 9

Section topic: Electrical engineering and fundamentals of electronics. (3 hours)
Lesson topic No. 27: Semiconductor devices.

Target: Familiarize yourself with semiconductor devices.

Lesson progress:
1. Organizational part 3 min.
a) Greeting.
b) Identification of absentees.
c) Repetition of the material covered.
d) Announcing the topic of the lesson. Record the topic of the lesson in notebooks.
e) Communicating the objectives and lesson plan to students.

2.Repetition of the covered material -7 min.

What are the main types of electrical installation work?

What are conductive materials?

Application of conductor materials?

3. Studying new material 10 min.

Semiconductor devices are called devices whose operation is based on the use of the properties of semiconductor materials

Semiconductor devices include :

-Integrated circuits (chips)

Semiconductor diodes (including varicaps, zener diodes, Schottky diodes),

Thyristors, photothyristors,

Transistors,

Charge-coupled devices

Semiconductor microwave devices (Gunn diodes, avalanche diodes),

Optoelectronic devices (photoresistors, photodiodes, solar cells, nuclear radiation detectors, LEDs, semiconductor lasers, electroluminescent emitters),

Thermistors, Hall sensors.

Main materials for the production of semiconductor devices are silicon (Si), silicon carbide (SiC), gallium and indium compounds.

Electrical conductivity semiconductors depends on the presence of impurities and external energy influences (temperature, radiation, pressure, etc.). The flow of current is determined by two types of charge carriers - electrons and holes. Depending on the chemical composition, pure and impurity semiconductors are distinguished.

Semiconductors

4. Practical work 18 min.
One way to do this is to measure the resistance with an ohmmeter between the emitter and collector terminals when connecting the base to the collector and when connecting the base to the emitter. In this case, the collector power source is disconnected from the circuit. If the transistor is working properly, in the first case the ohmmeter will show low resistance, in the second - on the order of several hundred thousand or tens of thousands of ohms.

Semiconductor diode - semiconductor device with one electrical junction and two terminals (electrodes). Unlike other types of diodes, the operating principle of a semiconductor diode is based on the pn junction phenomenon.

Semiconductor Diode Testing

When testing diodes using AMM, the lower measurement limits should be used. When checking a working diode, the resistance in the forward direction will be several hundred Ohms, and in the reverse direction - an infinitely large resistance. If the diode is faulty, the AMM will show a resistance close to 0 in both directions or a break if the diode breaks down. The resistance of transitions in the forward and reverse directions is different for germanium and silicon diodes.

5. Lesson summary 2 min.
6. Cleaning workplaces 5 min.

Physical properties of semiconductors Semiconductors are materials that, in terms of their specific conductivity, occupy an intermediate position between conductors and dielectrics. The main property of these materials is an increase in electrical conductivity with increasing temperature. Conducts electric current well These include metals, electrolytes, plasma... The most used conductors are Au, Ag, Cu, Al, Fe... They conduct electric current well These include metals, electrolytes, plasma... The most used conductors are Au, Ag, Cu, Al, Fe ... Practically do not conduct electric current These include plastics, rubber, glass, porcelain, dry wood, paper ... Practically do not conduct electric current These include plastics, rubber, glass, porcelain, dry wood, paper ... They are intermediate in conductivity position between conductors and dielectrics Si, Ge, Se, In, As Occupy an intermediate position in conductivity between conductors and dielectrics Si, Ge, Se, In, As

Physical properties of semiconductors R (Ohm) t (0 C) R0R0 metal semiconductor 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.

Electric current in semiconductors Semiconductors are substances whose resistivity decreases with increasing temperature. Semiconductors include silicon, germanium, selenium, etc. The bond between atoms is pair-electronic or covalent. At low temperatures, bonds are not broken

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

“Hole” When heated, the kinetic energy of electrons increases and the fastest of them leave their orbit. When the bond between the electron and the nucleus is broken, a free space in the electron shell of the atom. In this place a conditional positive charge is formed, called a “hole”. Si hole + + free electron

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, which are donor and acceptor Impurities Acceptor Donor p-type semiconductors p-type semiconductors n-type semiconductors n-type semiconductors

Hole semiconductors (p-type) In + Si The term “p-type” comes from the word “positive”, which denotes the positive charge of the majority carriers. This type of semiconductor, in addition to the impurity base, is characterized by the hole nature of conductivity. A small amount of atoms of a trivalent element (such as indium) is added to a tetravalent semiconductor (such as silicon). Each impurity atom establishes a covalent bond with three neighboring silicon atoms. To establish a bond with the fourth silicon atom, the indium atom does not have a valence electron, so it grabs a valence electron from the covalent bond between neighboring silicon atoms and becomes a negatively charged ion, resulting in the formation of a hole. The impurities that are added in this case are called acceptor impurities. indium

Electronic semiconductors (n-type) As Si The term “n-type” comes from the word “negative”, which denotes the negative charge of the majority carriers. This type of semiconductor has an impurity nature. An impurity of a pentavalent semiconductor (for example, arsenic) is added to a tetravalent semiconductor (for example, silicon). During the interaction, each impurity atom enters into a covalent bond with silicon atoms. However, there is no place for the fifth electron of the arsenic atom in saturated valence bonds, and it goes to the outer electron shell. There, it takes less energy to remove an electron from an atom. The electron is removed and becomes free. In this case, charge transfer is carried out by an electron, not a hole, that is this type Semiconductors conduct electric current like metals. Impurities that are added to semiconductors, causing them to become n-type semiconductors, are called donor impurities.

Donor impurities are impurities that donate an extra valence electron. Semiconductors with donor impurities have electronic conductivity and are called n-type semiconductors. Acceptor impurities are impurities that do not have enough electrons to form a complete covalent bond with neighboring atoms. Semiconductors with acceptor impurities have hole conductivity and are called p-type semiconductors.

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 electric field strength in the sample is zero, then the movement of 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.

Diode A semiconductor diode is a semiconductor device with one electrical junction and two terminals (electrodes). Unlike other types of diodes, the operating principle of a semiconductor diode is based on the pn junction phenomenon. The diode was first invented by John Flemming in 1904.

Types and applications of diodes Diodes are used in: converting alternating current into direct current, detecting electrical signals, protecting different devices from incorrect polarity switching switching high-frequency signals stabilizing current and voltage transmitting and receiving signals Transistor An electronic device made of semiconductor material, usually with three terminals, that allows input signals to control current in an 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.

Setting up and optimizing operating systems

Development of a physics lesson on the topic “electric current in semiconductors.” Lecture notes "Semiconductors" Lesson plan on the topic of semiconductor materials