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EEGR 215 Materials & Devices
Lab 2
Instructor: Dr Juan White Due
Date: October 3, 2016
With the help of a computer and a commercial software package such as Matlab to solve the
following problems:
1. Write a Matlab program to confirm that the ni versus T curve for Ge and Si graphed in
Figure 2.20 can be generated by employing the empirical fit relationships below. Check
over the temperature range of 275K ≤ T ≤ 375K.

2

 T  0.5928kT
ni(Si )  9.15  10 
 e
 300 

19

ni (Ge)  1.76  1016 T  2 e
3
0.392
kT
eqn. 1
eqn. 2
2. Generate a MATLAB program to compute and plot the Fermi function, f(E), and 1- f(E)
versus ΔE = E-Ef for values of ΔE that is over the range of -0.5eV ≤ ΔE ≤ 0.5eV for
varying temperature settings where Temperature = 150, 250, 350, 450 and 550K. Make
sure that each f(E) versus ΔE curve at each temperature is superimposed on the same
plot. Discuss what you see in your plots as the Fermi function, f(E), and 1-f(E) varies
with temperature and energy.
3. Consider GaAs at T = 300K with Nd =0. (a) Plot the position of the Fermi energy level
with respect to the intrinsic Fermi energy level as a function of the acceptor impurity
concentration over the range of 1014 ≤ Na ≤ 1017 cm-3. (b) Plot the position of the Fermi
energy level with respect to the valence-band energy over the same acceptor impurity
concentration given in part (a).
4. The temperature of a sample of Ge is T = 300K and the acceptor doping concentration is
Na = 0. Plot the minority carrier concentration (on a log-log plot) versus Nd over the
range 1015 ≤ Nd ≤ 1018 cm-3

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