Benha University
2nd Year Mech. Power
Faculty of Engineering – Shoubra
Subject: Electronic Engineering
Mechanical Engineering Department
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Sheet (4)
1. Calculate the intrinsic carrier density in germanium, silicon and gallium arsenide
at room temperature (300 K). Repeat at 100 ° C. Assume that the energy band gap
is independent of temperature and given by the values provided below.
Name
Energy gap
Intrinsic carrier density at
300 K
Intrinsic carrier density at
100 ° C
Ge
0.66 eV
Si
1.12 eV
GaAs
1.424 eV
2. Consider an n-type silicon semiconductor at T = 300 K in which Nd = 1016 cm-3
and NA = 0.The intrinsic carrier concentration is assumed to be ni = 1.5 x 10 10
cm-3. Determine the thermal equilibrium electron and hole concentrations for the
given doping concentration.
3. Find the hole concentration in silicon at T=27 °C, The electron concentration is
n=1×105 cm-3 and the intrinsic carrier concentration is 1.5×1010 cm-3.
4. Consider a gallium arsenide sample at T = 300 K with doping concentrations of
NA= 0 and ND =1016 cm-3 and ni = 1.8×106 cm-3. Assume complete ionization and
assume electron and hole mobility given in Table below. Calculate the drift current
density if the applied electric field is E = 10 V/cm.
5. Consider a sample of silicon at T = 300 K doped at an impurity concentration of
NA =5*1016 cm-3 and ni = 1.5×1010 cm-3.Calculate the current density (J).
E=8V/cm.