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Quiz 01
ID#
Name:
Part I: True and False
1. A resistor (shown on the right hand
side) is formed from a block of P-Type
semiconductor material which is
uniformly doped at
N A  2  1016 donor / cm 3 .
a) Considering the total net charge in
the material after being doped the
material is positively charged.
b) Assuming operation at T  273K , with the applied voltage V  3V , the drift
current for holes and electrons are all zero.
c) The diffusion current for holes is zero but the diffusion current for electrons is
not zero.
2. The following figure shows the minority carriers distribution of a PN junction
under the forward bias. Indicate whether each of the following statements is true of
false based on the information you learn form the figure.
a) The doping concentration of N side is higher than P side.
b) The electrons diffusion current flow is in the direction of x .
c) The diode current flow is in the same direction as the diffusion current flow.
d) The depletion width x2  x1 implies the doping concentration N A N D .
Minority concentration
n p (x )
pn (x)
n po
x2
pno
x1
x
Part II: problems
1. Consider a Si semiconductor PN junction with N and P doping concentration of
N A  1016 carriers
cm
3
and N D  5  1016 carriers
cm
3
.(  s  1.04  10 12 F
cm
)
a) Find the built-in potential (or barrier voltage) V0  ? .
b) What is the depletion width at zero bias Wdep  ?
c) What is the maximum electric field at zero bias E max  ?
2. The following figure shows a silicon bar that is subjected to electron injection from
the left.
5 1016 carriers
electrons
cm3
Silicon
0m n  1.45 1010 carriers
i
11016 carriers
cm 3
2 m
cm3
a) Determine the electron diffusion current density J ndiff ( Dn  32cm 2 / s ).
b) Determine the hole diffusion current density J pdiff ( D p  12cm 2 / s ).
c) Determine the electric field E at x  2 m (  n  1350cm 2 / V  s
 p  480cm 2 / V  s ).
d) Determine the electron drift current density J ndrift at x  2 m .
e) Determine the total current I .