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KTU B.Tech S3 model Questions for Solid State Devices

 

KTU B.Tech S3 model Questions for Solid State Devices

MODEL QUESTION PAPER Prepared by ktubtechquestions.com

THIRD SEMESTER B.TECH  DEGREE EXAMINATION  JANUARY 2017

EC 203: SOLID STATE DEVICES

Time: 3 Hrs                                                                                                                      Marks: 100

PART A

( Answer any One from 1 and 2. Q.No: 3 is Compulsory )

i) Draw the energy level diagram of an intrinsic semiconductor, n-type semiconductor and  p-type semiconductor. (3)

ii) What are different carrier scattering mechanisms? (2)

 iii) Compute the number of holes in a heavily doped (n = 1×1018/cm3) n-type semiconductor material with intrinsic concentration ni =1.5×1010/cm3. (2)

 iv) For a GaAs semiconductor (Eg = 1.43 eV), determine the minimum wavelength of an incident photon that can interact with a valence electron and elevate to the conduction band. (3)

OR

2.

i) Define quasi Fermi level. When do they exist? (2)

ii) What is diffusion capacitance? Is it a capacitance that is always present in junctions? (2)

iii) Derive Einstein Relation.                                                                                        (6)

 

3.

    i) Determine the value of Hall electric field in the case of a Ge sample of length 0.1 cm, width of 0.01cm and          thickness of 0.001cm, doped with 1017 acceptor atoms/cm3. Assume that the current flowing through the                sample is 5mA and the magnetic field applied is 1 μT. (10)

   ii) Derive the continuity equation. (10)

 PART B

(Answer any One from 4 and 5. Q.No: 6 is Compulsory)

4   i) Discuss briefly the temperature dependence of diode V-I characteristics.(2 marks)

   ii) Draw the energy band diagram of a metal semiconductor contact and explain its working.

(8 marks)

OR

5   i) Compute the number of holes in a heavily doped (n = 1×1018/cm3 ) n-type semiconductor material with                        intrinsic concentration ni =1.5×1010/cm3 (2 marks)

     ii)The forward current of a Silicon Schottky barrier diode and a pn junction diode are 1mA    each. The reverse                saturation currents of both the diodes are 10×10-7 A. Compute the value of the reverse saturation current of                  the pn junction diode if the difference in the forward voltages of the two diodes is 0.25 V.  (8  marks)

6     i) Discuss the construction and V-I characteristics of a Schottky diode (10 marks)

      ii) Discuss the switching transients in a pn diode. (10 marks)

PART C

(Answer any One from 7 and 8. Q.No: 9 is Compulsory)

7   i) Describe the switching characteristics of a BJT. (10 marks)

    ii) Compute the base width required to achieve a base transport factor βT=0.95. Given that DB=10cm2 /s and             τB=10-7 s. (10 marks)

OR

8    i) Identify and explain the two modes of operation of the MOSFET. (10 marks)

     ii) An n-type MOSFET has W = 25µm, L = 2.5µm, tOX = 400Å, µn = 800cm2 /Vs and VT=0.8V. Compute the                 value of ID for VGS=1 V. (10 marks)

9    i)Derive a relation for the threshold voltage of a MOS capacitor (10 marks)

     ii) A 0.3 µm single crystal of silicon is subjected to incident light normal to the surface having power of 20mW.               Given the attenuation factor for silicon at the frequency of the light is 5×104 cm-1 and the index of refraction                 of  silicon is 3.5. Determine the power absorbed by the crystal. (10 marks)

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