Reading. Doping of semiconductors

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DOPING OF SEMICONDUCTORS

1. Part of this text is missing. Complete the sentences 1 – 10 with the phrases A – J. Use the information from the text about the types of semiconductors to help you. Put the verb “To be” in brackets in the correct form.

1) There (to be) ……………

2) Intrinsic semiconductors ………….

3) They (to be) ………………

4) Doping (to be) ……………

5) Extrinsic semiconductors ………………

6) Dopant (to be) ……………….

7) The materials chosen as suitable dopants …………

8) Dopants that produce the desired controlled changes (to be)………….

9) N-type semiconductors (to be) ……………

10) P-type semiconductors (to be) ……………

A. doped with acceptor impurities.

B. the process of deliberately introducing other elements into a crystal.

C. intrinsic and extrinsic semiconductors.

D. have good conductivity.

E. generally insulators.

F. the element introduced by doping.

G. classified as either electron acceptors or donors.

H. doped with donor impurities.

I. do not conduct electric current.

J. depend on the atomic properties of both the dopant and the material to be doped.

2. Find the synonyms to the adjectives: intrinsic and extrinsic.

3. Match the pictures in Fig. 1.4 with the descriptions 1-3.

Fig. 1.4. Crystal lattices of undoped (pure) and doped (p-type, n-type) semiconductors.

1) It is an extrinsic semiconductor which is obtained by doping the impurity atoms of the V group in the periodic table of elements. The impurity atoms added, provide extra electrons in the structure and are called donor atoms. The electrons are majority carriers and holes are minority carriers.

2) Each circle represents a silicon atom, and the lines between the atoms represent the shared electrons. Each of the four valence electrons in each silicon atom is shared with one neighboring silicon atom. Thus, each silicon atom is bonded with four other silicon atoms.

3) It is an extrinsic semiconductor which is obtained by doping the impurity atoms of the III group in the periodic table. The impurity atoms added, create holes in the structure and are called acceptor atoms. The holes are majority carriers and electrons are minority carriers.

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