# EC 203 SOLID STATE DEVICES KTU MODAL QUESTIONS FOR SECOND YEAR S3

## APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY

SOLID STATE DEVICES QUESTION PAPERS

PART A

1. Derive an expression for the electron current in the n-type material of a forward biased p-n junction?

2. Define diffusion length of a hole? Mention the relation between carrier life time and diffusion length of hole?

3. Define luminescence? Mention different types of luminescence?

4. For a P+N junction diode, which region is heavily doped? Also prove with suitable equations, which region among P side depletion region or N side depletion will be greater?

5. Draw the energy band diagrams for a PN junction in a) equilibrium b) Forward biased c) Reverse biased cases?

PART B

(Answer Any Two Questions)

6. Derive the continuity equation?

7. Explain the quasi Fermi level with suitable equations and figures?

8. Derive the diode equation?

9. An abrupt Si p-n junction has Na=10^18 cm^-3 on one side and Nd=5*10^15 cm^-3 on the other side.

The junction has a circular cross section with diameter of 10μm.

Calculate contact potential, Xno, Xpo, depletionregion
width(W), Q+ and €o(electric field)? Given Ɛr=11.8, Ɛ0=8.854*10^-14.