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- Solid State Devices - SSD
- 2017
- PYQ
**Biju Patnaik University of Technology Rourkela Odisha - BPUT**- Electronics and Instrumentation Engineering
- B.Tech
**1440 Views**- 21 Offline Downloads
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Registration No : Total Number of Pages : 02 B.Tech PEI3D001 3rd Semester Regular Examination 2017-18 SOLID STATE DEVICES BRANCH : AEIE, EIE, IEE Time : 3 Hours Max Marks : 100 Q.CODE : B1245 Answer Question No.1 and 2 which are compulsory and any four from the rest. The figures in the right hand margin indicate marks. Assume suitable values wherever necessary Q1 a) b) c) d) e) f) g) h) i) j) Q2 a) b) c) d) e) f) g) h) i) j) Q3 a) b) Answer the following questions: When P-type substance is connected with positive and N-type is connected with negative terminal then P-N junction diode is in ..................Bias condition. If temperature increases then conductivity of a semiconductor………….. The pinch-off voltage of JFET…………. with increasing channel width. In enhancement type MOSFET the applied gate to source voltage must be …………..….than the threshold voltage for the device to conduct. The pn junction region which is devoid of mobile charges is called the ……..… region. Ionization within a P-N junction causes a layer on each side of the barrier called the………………………. Layer. In ………………….region both the collector-base and base-emitter junctions of the BJT are forward-biased. The amount of time between the creation and disappearance of a free electrons is called……………………………………. The drain current in MOSFET ……………. when VDS becomes equal to the VGSVt. …………………..is the example of a direct band gap semiconductor. (2 x 10) Answer the following questions: An electron has a kinetic energy of 20 meV. Determine the de Broglie wavelength. An electron's energy is measured with an uncertainty of 1.2 eV. What is the minimum uncertainty in time over which the energy is measured'? The lowest energy of a particle in an infinite potential well with a width of 100 Å is 0.025 eV What is the mass of the particle? List the boundary conditions for solutions to Schrodinger's wave equation. Determine the position of the intrinsic Fermi level with respect to the centre of the Band gap in GaAs at T = 300 K. What do you understand by Surface Inversion in MOSFETs? What do you understand by Schottky Effect? What is the significance of the n0p0 product? For hole mobility of 500 cm2/V-s, calculate the hole diffusion coefficient. What is the cause of junction capacitance in PN junctions? (2 x 10) What do you understand by Degenerate and Nondegenerate Semiconductors? Draw the Energy-band diagram of a compensated semiconductor showing ionized and un-ionized donors and acceptors. What do you understand by the term compensated? Consider a compensated GaAs semiconductor at T = 300 K doped at Nd=5 x1015/cm3 and Na = 2 x 1016/cm3. Calculate the thermal equilibrium electron and hole concentrations. (5) (10)

Q4 a) b) Differentiate between drift and diffusion currents. Describe the concept of excess generation and recombination. (5) (10) Q5 a) Why is an electric field formed in the space charge region? Why is the electric field a linear function of distance in a uniformly doped pn junction? Where does the maximum electric field occur in the space charge region? A silicon pn junction at T = 300 K with zero applied bias has doping concentrations of Nd= 5 x 1016/cm3 and Na= 5 x 1015/ cm3. Determine xn, xp,W, and |Emax|. (10) Differentiate between Homojunctions and Heterojunctions. Give suitable illustrations and examples in each case. Describe what is meant by an ohmic contact. (10) Describe the physical mechanism of base width modulation and its effect on the current-voltage characteristics of the BJT. Sketch the simplified small-signal hybrid-pi equivalent circuit of the transistor biased inthe forward-active mode. (10) b) Q6 a) b) Q7 a) b) (5) (5) (5) Q8 a) b) With suitable illustrations describe the basic MISFET operation. Discuss the I-V characteristics of the MOSFET when biased in the nonsaturation and saturation regions. (10) (5) Q9 a) b) Elaborate on any two modes of operation of the MOSFET. An n-type MOSFET has W = 25µm, L = 2.5µm, tOX = 400Å, µn = 800cm2 /Vs and VT=0.8V. Compute the value of drain current, ID for VGS=1 V. (10) (5)

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