1. Describe and explain how electrical charge is carried through

(a) a good conductor

(b) an insulator

(c) intrinsic semiconductor.

Your answer should include the name and polarity of the charge carriers involved.

2. Explain how an intrinsic semiconductor can be doped to become a p-type or n-type material. Describe and explain the movement of electrical charge through p-type and n-type semiconductors. Mention all charge carriers and their relative contribution to the conduction process.

3. For each of the following semiconductor devices describe its structure and electrical operation:

Devices:

- diode

- field effect transistor

- bipolar transistor.

4. FIGURE 1 shows a semiconductor resistor formed by a p-type diffusion into an n-type background. The resulting p-type material was found to have a sheet resistance of 100 Ω.

Fig. 1

Estimate:

(a) the resistance of the resistor

(b) the required depth of the p-type diffusion if the p-type layer has a resistivity of 2 × 10^-4 Ωm.

5. Explain what is meant by a MOSFET's threshold voltage and describe a method by which it could be measured.