Download Tutorial 4. Carrier transport and Excess Carrier Phenomena

1.
Calculate the drift current density induced in a semiconductor for a given applied electric field.
Consider a silicon semiconductor at T = 300 K with an impurity doping concentration of
Nd = 1016 cm-3 and Na = 0. Assume electron and hole mobilities to be n = 1350 cm2/V-s and
p = 480 cm2/V-s. Calculate the drift current density for an applied electric field of
 = 35 V/cm.
2.
Consider a gallium arsenide sample at T = 300 K with doping concentrations of Nd = 1016 cm-3
and Na = 0. Assume electron and hole mobilities to be n = 8500 cm2/V-s and p = 400 cm2/Vs. Calculate the drift current density if the applied electric field is  = 10 V/cm.
3.
Determine the required impurity doping concentration in silicon at T = 300 K to produce a
semiconductor resistor with specified current-voltage characteristics. Consider a bar of silicon
uniformly doped with acceptor impurities. For an applied voltage of 5 V, a current of 2 mA is
required. The current density is to be no larger than Jdrf = 100 A/cm2. Find the required crosssectional area, and doping concentration.
4.
For a particular silicon semiconductor device at T = 300 K, the required material is to be n
type with a resistivity of  = 0.1 -cm. Determine the required impurity doping concentration
and the resulting electron mobility.
5.
Three scattering mechanisms are present in a particular semiconductor material. If only the
first scattering mechanism were present, the mobility would be 1 = 2000 cm2/V-s, if only the
second mechanism was present, the mobility would be 2 = 1500 cm2/V-s, and if only the
third mechanism were present, the mobility would be 3 = 500 cm2/V-s. What is the net
mobility?
6.
A silicon semiconductor is in the shape of rectangular bar with a cross-sectional area of
10 m x 10 m, a length of 0.1 cm, and is doped with 5 x 1016 cm-3 arsenic atoms. The
temperature is T = 300 K. Determine the current if 5 V is applied across the length.