SOLID STATE DEVICES (ECL 1301)
Assignment (Dated: 18/09/2022)
1. For an intrinsic semiconductor, the total mobility is 1000 cm 2/V-s and the mobility
due to the holes is 600 cm2/V-s. Nc = Nv = 1019 cm-3. The measured conductivity of this
semiconductor at 300 K is 10-6 (Ω-cm)-1. What is the conductivity at 500 K?
2. A n-type semiconductor is doped with 1 x 1015 cm-3 donor atoms. Assume complete
ionization of donor atoms and N a= 0. The effective density of states Nc = Nv = 1.5 x 1019
cm-3 and are independent of temperature. The device has equilibrium electron
concentration as 1.01 x 10 15 cm-3 at 400 K. Find the bandgap energy of this device.
3. A particular intrinsic semiconductor has a resistivity of 50 Ω-cm at 300 K and 5 Ωcm at 330 K. Neglecting the change in mobility with temperature, determine the
bandgap energy of the semiconductor.
4. A semiconductor in thermal equilibrium, has a hole concentration of 10 16 cm-3 and
an intrinsic concentration of 1010 cm-3. The minority carrier lifetime (or
recombination lifetime) is 2 x 10-7 s. Determine the thermal equilibrium
recombination rate of electrons. Also compute the change in recombination rate of
electrons if an excess electron concentration of 10 12 cm-3 exists.
5. Consider a uniformly doped Si PN junction diode with intrinsic carrier
concentration of 1.5 x 1010 cm-3. The doping concentrations are Na = 5 x 1017 cm-3 in
p-type region and Nd = 1017 cm-3 in n-type region. Calculate the built-in potential when
a reverse bias voltage of 5V is applied across the diode at 300 K. Also calculate the
depletion width and maximum electric field at the junction under this condition.
6. An abrupt Ge PN junction diode with intrinsic carrier concentration of 2.5 x 10 13
cm-3 is uniformly doped with Na = 5 x 1018 cm-3 in p-type region and Nd = 2 x 1016 cm3 in n-type region. The junction area is 6 x 10 -4 cm2. An inductance of 2.2 mH is placed
parallel to the junction. Calculate the resonant frequency of the circuit under reverse
bias condition with applied voltage of 10V.
7. A plane in a crystal lattice intercepts the x, y, z axes at 2, 4, 6 units. What are the
Miller indices of this plane?
Last date of submission of this assignment alongwith the previous assignments
is 30/09/2022 at 5 p.m.