IV. Ответьте на следующие вопросы, пользуясь информацией из текста

1. Why is a semiconductor often referred to as an insulator?

2. What are conductors in science and engineering?

3. How can materials be classified?

4. Under what condition will electric charge move?

5. What is the resistivity of the material?

6. Why do non-conducting materials resist the flow of electric current?

7. Transistors have dynamically controllable conductivity , don’t they?

8. What is the resistance of semiconductors modified by?

V. Переведите на русский язык цепочки существительных. Обратите внимание, что последнее слово является опорным

Valence electrons, a standard mass, a current flow, room temperature, conduction bard, impurity atom, semiconductor device, photoemission process

VI. Дополните следующие предложения фактами из текста

1. Insulators are materials which …

2. Apart from conductors, materials are classified according to …

3. All conductors contain …

4. Most familiar conductors are …

5. Non-conducting materials lack …

6. a semiconductor is …

7. Semiconductors are very similar to …

8. Transistors are the building blocks of …

VII. Выделите суффиксы слов с одинаковым корнем и переведите на русский язык следующие группы слов

To achieve –achievement – achievable

To apply – appliance- application – applying – applied

To resist – resistance – resistivity

To conduct – conductance – conductivity

To divide – dividing – division

To create – creative – creation

VIII. Объясните, почему

1. we need conductors and insulators

2. a perfect insulator is not possible

3. design details vary widely

4. we mostly use copper conductors

5. semiconductors are important in modern technology

IX. Разделите текст на логические части. Озаглавьте каждую часть и изложите её содержание в 3-4 предложениях на английском/ русском языках

X. Прокомментируйте ту часть текста, которая показалась вам наиболее интересной

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Прочитайте текст и определите его основную идею

Carrier generation and recombination

When ionizing radiation strikes a semiconductor, it may excite an electron out of its energy level and consequently leave a hole. This process is known as electron–hole pair generation. Electron-hole pairs are constantly generated from thermal energy as well, in the absence of any external energy source.

Electron-hole pairs are also apt to recombine. Conservation of energy demands that these recombination events, in which an electron loses an amount of energy larger than the band gap, be accompanied by the emission of thermal energy (in the form of phonons) or radiation (in the form of photons).

In the steady state, the generation and recombination of electron–hole pairs are in equipoise. The number of electron-hole pairs in the steady state at a given temperature is determined by quantum statistical mechanics. The precise quantum mechanical mechanisms of generation and recombination are governed by conservation of energy and conservation of momentum.

As the probability that electrons and holes meet together is proportional to the product of their amounts, the product is in steady state nearly constant at a given temperature, providing that there is no significant electric field (which might "flush" carriers of both types, or move them from neighbour regions containing more of them to meet together) or externally driven pair generation. The product is a function of the temperature, as the probability of getting enough thermal energy to produce a pair increases with temperature, being approximately 1/exp(band gap / kT), where k is Boltzmann's constant and T is absolute temperature.

The probability of meeting is increased by carrier traps – impurities or dislocations which can trap an electron or hole and hold it until a pair is completed. Such carrier traps are sometimes purposely added to reduce the time needed to reach the steady state.

Lesson 5

Electromotive force