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Reg No.:_ Name:

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
THIRD SEMESTER B.TECH DEGREE EXAMINATION(R&S), DECEMBER 2019
Course Code: EC203
Course Name: SOLID STATE DEVICES (EC,AE)
Max. Marks: 100 Duration: 3 Hours

PARTA
Answer any two full questions, each carries 15 marks. Marks
1 8) Derive the expression for conductivity and mobility of carriers in a (7)
semiconductor subjected to an electric field.

b) Explain the temperature dependence of carrier concentration in extrinsic (3)
semiconductors.
c) Calculate the hole and intrinsic carrier concentrations. Sketch band (5)
diagram. 11-10 3/௯. 72510100, Eg=2eV, T=900K, ‏دص 107ص0‎
2 a) Derive Einstein’s relation. (6)
b) Explain why indirect recombination is a slow process. (4)
c) A Si sample is doped with 10'°/cm? In atoms and ೩ certain number of shallow (5)

donors. The In acceptor level is 0.16eV above Ey and ‏ہب‎ is 0.26eV above Ey at
300K.How many In atoms are un-ionised?

3 9) Derive the expression for electron, hole and intrinsic concentrations at (8)
equilibrium in terms of effective density of states. Formulate the relation between
these concentrations at equilibrium.
b) An n-type Si sample with Nd = 1015 cm? is steadily illuminated such that 8೦0 ಎ... (7)
107 EHP/cm’s. If Ta= Tp = lus for this excitation, calculate the separation in the
quasi-Fermi levels, (Fn - Fp).

PART छ
Answer any two full questions, each carries 15 marks.
4 ஐ Derive ideal diode equation. State any two assumptions used. (10)

b) Draw the potential, charge density and electric field distribution within the (5)
transition region of an abrupt pn junction with Nd5 லு Illustrate how a metal — n type contact behave as rectifying contact and ohmic (10)
contact with supporting energy band diagram.
b) 1 metal with a work function of 4.6 € V is deposited on Si (electron affinity of (5)
4 eV) and acceptor doping level of 105 ണ്‌. Draw the equilibrium band diagram
and mark off the Fermi level, the band edges, and the vacuum level. Is this a
Schottky or ohmic contact, and why?
6 a) Illustrate the operation of a tunnel diode with supporting diagrams and explain (10)
its VI characteristics

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