971 Quiz 01

Quiz 01
1. (15%) Consider n-type GaAs at T = 300 K doped to a concentration of Nd =
2 × 1016 cm−3 . Assume mobility values of μn = 6800 cm2/V–s and μp =
300 cm2/V–s. Determine the applied electric field that will induce a drift
current density of 175 A/cm2.
2. (40%)The following figure shows a silicon bar that is subjected to holes
injection from the right.
a. Determine the minority carrier concentration at x  0 .
b. Determine the minority carrier concentration at x  4 m .
c. Determine the electron diffusion current density J ndiff ( Dn  32cm / s ).
d. Determine the hole diffusion current density J pdiff ( D p  12cm 2 / s ).
e. Determine the electric field E at x  0 m (  n  1350cm / V  s
 p  480cm 2 / V  s ).
f. Determine the electron drift current density J ndrift at x  0 m .
g Determine the hole drift current density J pdrift at x  0 m .
h. Determine the total current density
i. Which type the silicon bar is?
3. (45%) True and false
(1) GaAs is the most widely used semiconductor material because of its
stability at high temperatures.
(2) The depletion layer in a p-n junction contains few electrons and holes.
(3) There are two types of carriers in a semiconductor. The holes and
electrons diffusion current direction is opposite to that of the applied electric
(4) The conductivity in pure semiconductors increases as temperature goes up.
(5) Group V elements are used as dopants to produce N-type semiconductors,
because they have one more electron than the original Group IV material.
(6) N-Type semiconductor formed by diffusing group 5 impurities.
(7) An electric field pulls electrons and holes current flow in the opposite
(8) As the temperature increases, more electrons can be promoted to the
covalence band.
(9) Forbidden energy gap is the gap between conduction band and valance
band. In insulator, Forbidden energy gap is very large.