M.Sc- 4th Sem Electronic Materials(Vidyasagar University, Midnapore, West Bengal-2011)

M.Sc- 4th Sem Electronic Materials(Vidyasagar University, Midnapore, West Bengal-2011)

4th Semester Examination

ELECTRONIS

PAPER—EL-2203

Full Marks : 40

Time : 2 Hours

The figures in the right-hand margin indicate full marks.

Candidates are required to give their answers in their own words as far as practicable.

Illustrate the answers wherever necessary.

Answer Q. No. I and any three from the rest.

1. Answer any Fivequestions :       2 x5

(a)         Discuss the physical significance of Fermi Golden Rule.

(b)         Amongst quantum dot and quantum wire lasers which one requires less threshold current and why ?

(c)         Distinguish between graded gap and stair case APDs.

(d)        Explain quasi-equilibrium condition of a semiconductor laser.

(e)         Mention the essential difference between photo conduction and photoemission.

(i)       Discuss the merits of MQW laser compared to QW laser.  

2. (a) What do you mean by perturbation? What an degenerate and non-degenerate systems?

(b) In case of time independent perturbation ¿aduce thi expression of ñrst order perturbation in wave function In'), 5+5

3. (a) Expìain why microwave emission of stipulated type be obtained more easily than lasef emission.What are the advantages of NH3 MASER?

(b) Using time dependent perturbation theory explain the phenomena of absorption and emission. 2+3+5

(c) Discuss with a neat energy band diagram the mechanism of a semiconductor laser.

4. (a) What are the drawbacks in a homojuncuor semiconductor laser?

(b) We can get better optical confinement and lowel threshold current by introducing hetero-junction

Explain why ?

(c) Díscuss how threshold current can be reduced i2: quantum well.

5. (a) How that the density of state function in tw; dimension is inde-pendent of energy.

(b) Show graphically how density of staàes for quantum differs for' 'the bulk devices. 3+(5+2)

(c) how solid sîate photo multiplication could be obîained in a super lattice APD.

6. (a) Compare p-n photodiode and pfien photodiode as regards their performance characteristics.

(b) Menüon different noises Iiresent in APDs. 5+3+2