물리전자공학 1, 과제 2
1. The hole concentration is given by exp cm for ≥ and the
electron concentration is given by × exp cm for ≤ . The
values of and are × cm and cm, respectively. The hole and
electron diffusion coefficients are cms and cms , respectively. The total
current density is defined as the sum of the hole diffusion current density at
and the electron diffusion current density at . Calculate the total
current density.
2. Consider a semiconductor in thermal equilibrium (no current). Assume that the
donor concentration varies exponentially as exp over the range
≤ ≤ where and is a constant. (a) Calculate the electric field as
a function of for ≤ ≤ . (b) Calculate the potential at when the
potential at is zero.
3. An abrupt silicon pn junction at zero bias has dopant concentrations of
cm and × cm at K . (a) Calculate , , , and
the magnitude of the peak electric field. (b) Sketch the equilibrium energy band
diagram for the junction.
4. Consider a uniformly doped silicon pn junction at K . The junction
capacitance at zero bias is and the junction capacitance with a 10 V
reverse bias voltage is . The ratio of the capacitances is . Also
under reverse bias, the space charge width into the region is 20% of the total
space charge width. Determine , , and .
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