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Quiz 2 ELEC 4705Wed. Oct. 19 2016

1. (10 marks) Semiconductors

(a) (2 marks) What are the two types of charge carriers present in a semiconductor?

(b) (8 marks) The equation for carrier density in a semiconductor is given by:

n =∫ +∞

0g(E)f(E,EF , T )dE (1)

• What are E and EF ?

• What do we call g(E) and what does it represent?

• What do we call f(E) and what does it represent?

• What therefore does the product G(E)f(E) represent?

• What is the integral “doing”?

• Why can we integrate to ∞?

ELEC 4705 Electronic Properties of Materials Quiz 2

2. (10 Marks) Semiconductors

(a) What is difference between intrinsic and extrinsic semiconductors? What is thechief advantage of extrinsic semiconductors?

(b) What is the source of resistance in a semiconductor? Why does it produce resis-tance?

2 Oct 19, 2016

ELEC 4705 Electronic Properties of Materials Quiz 2

3. (10 marks) Light and Materials

(a) What are the three electron/photon events that can occur in a semiconductor?Briefly describe them. (Pictures!)

(b) What does the optical absorption coefficient α for a material represent?

i. Which of the three processes in part a) can be described by α. What would beits sign in each case?

ii. If light is incident on a material and α is positive how does the intensity of thelight vary as it travels through the material?

3 Oct 19, 2016