Semiconductor Devices — DU B. Sc. (Hons) Electronics Previous Year Question Papers

(b) Explain the structure of semiconductor-controlled rectifier (SCR) and further explain its characteristics. (c) Explain the structure and working of IGBT (Insulated Gate Bipolar Transistor). (f) Draw the structure of a p-channel MOSFET. rectifying contacts? Explain in brief. reverse bias junction. Fermi level from the bottom of the conduction per cm. Find the carrier concentration and the (b) A silicon ingot is doped with 10'8 arsenic atoms (6) that the Fermi level is close to middle of the band densities in an intrinsic semiconductor. Show (a) Derive an expression for electron and hole (3) of a p-n-p transistor. Also draw its symbol. (3) (e) Draw the doping profile along the block diagram (3) (d) What is the difference between ohmic and (3) (c) Draw the energy band diagrams of a forward and (3) diagrams of n type and p type semiconductor. extrinsic semiconductor. Draw energy band (b) Explain the difference between intrinsic and flowing in it. equilibrium. solar cell. regions of operation of the MOSFET. (a) Draw the structure of MOSFET. Based upon configuration and explain its variation. (ii) B=250, 1B=2uA (i) B=150, 1=3mA band at room temperature (300 K). The value of KT at 300K is 0.026eV and N, =2.86 x 1019 cm-? and n= 9.65 × 10°cm 3. (c) Describe various generation and recombination processes with suitable diagrams. How will you explain the lifetime of excess number of carriers? (a) Explain the phenomena of drift and diffusion of charge carriers in semiconductors. Derive Einstein relationship. (b) What is Hall effect? Explain its physical significance. (c) Express conductivity and resistivity of an intrinsic semiconductor in terms of mobility. Find the room temperature resistivity of an n type silicon doped with 10'7 phosphorus atoms per em? with drift velocity equals to 1.95 × 10' cm/s and applied electric field of 1.5kV/cm. Name a device which functions on this effect. for and abrupt and linearly graded junctions? diode? How does it vary with the applied voltage (b) What is depletion capacitance in a p-n junction voltage characteristics of a diode qualitatively. 5. (a) Give ideal diode equation and explain the current calculate the built in potential at 300K. junction at thermal equilibrium. no bias condition. two regions. Assume ni equal to 1.5 × 10'' cm?, 5x × cm cm? and No equal to x x cm em in the (c) A p-n junction has doping density N, equal to (6) constant (independent of x) in case of a p-n (b) Show that show that the Fermi level remain (6) junction and one-sided abrupt p-n junction under depletion width in the depletion region of p-n 4. (a) Draw the necessary diagrams for charge density,