Electronics > EXAM > EECS 170A Electronics I Midterm-II Exam Solutions (All)

EECS 170A Electronics I Midterm-II Exam Solutions

Document Content and Description Below

EECS 170A Midterm-II Practice Questions Room temperature T=300K q = 1.6 ×10-19C C m0 = 9.11 × 10 -31 kg kB = 1.38 × 10 -23 m2 kgs-2 K-1 or 8.6173 × 10-5 eVK-1 h = 6.63×10-34 J⋅s or 4.1357 × 10 -15 eVs ℏ = 1.05 ×10-34 J·s or 6.5821 × 10-15 eV s Å= 10-10 m 1. True or false ……Resistivity is primarily dependent on NA in a strongly p-type semiconductor. (T) ……Inside a semiconductor, electrons will continue to accelerate indefinitely within an electric field. (F) ……The mobility of free electrons in a compensated semiconductor is the same as in an intrinsic semiconductor. (F) …… In a p-type semiconductor, the majority of carriers are electrons. (F) …… A semiconductor can have only one type of impurity dopant at a time. (F) …… In an n-type semiconductor, the low level injection condition is n≅n0 (T) ……Quasi-Fermi levels are used to specify the carrier concentrations inside a semiconductor under equilibrium conditions. (F) ……Diffusion current is the net carrier flow caused by random thermal motion when a concentration gradient exists.. (T) ……The presence of an electric field in a semiconductor material causes energy band bending. (T) ……The drift current density in a conductor is directly proportional to the applied electric field, and resistivity is the proportionality constant. (F) ……The Einstein relation indicates that the ratio of the diffusion coefficient 𝐷 to the mobility 𝜇 is independent of temperature. (F) ……A semiconductor can be doped with both donor and acceptor impurities at the same time. (T) …… The Fermi level in an intrinsic semiconductor lies closer to the conduction band than to the valence band. (F) 2. Consider an n-type silicon semiconductor where the dominant electron scattering mechanisms are phonon scattering and ionized impurity scattering. The temperature dependence of each scattering mechanisms mobility component is as follows: Phonon scattering: Mobility due to phonon (lattice) scattering, 𝜇ph , follows 𝜇ph ∝ T-2.5 Impurity scattering: Mobility due to ionized impurity scattering, 𝜇imp , follows 𝜇imp ∝ T1.5 At T=300K: 𝜇ph=1800 cm2/V-s and 𝜇imp=2700 cm2/V-s. (a) Calculate the effective mobility 𝜇n at 300K. (b) Determine the effective mobility 𝜇n at an elevated temperature of 600 K. (c) As the electric field E in the semiconductor is increased. electron velocity saturates at a critical strength Esat=104 V/cm with a saturation velocity 𝑣sat= 107 cm/s. What is the electron drift velocity for an applied field of E=5000 V/cm and E=50000 V/cm at 300K? Solution:

[Show More]

Last updated: 5 hours ago

Preview 3 out of 12 pages

Buy Now

Instant download