University of Pennsylvania
ESE 521 The Physics of Solid State Energy Devices
March 25, 2013
Prof. C. R. Kagan
Exam #2
** Remember to label axes, drawings etc. in all of you work and include all units.
Assume E
i
is in the middle of the gap (no need to calculate any corrections).
1. You have a GaAs pn step junction held at 300K with an area A=10-4cm2and minority carrier lifetimes τN=5x10-9s and τP=3x10-6s. The pn junction has the following electric field distribution: (74 points) A. Assume you have an ideal diode. i. Calculate NAand ND. (6 points) ii. What is the built-in potential? (3 points) iii. What is the applied bias VAgiven the electric field distribution? (5 points) iv. Draw a plot for the carrier concentrations as a function of distance for the calculated applied bias in part (iii). Label the carrier concentrations relative to their thermal equilibrium values. Calculate the minority carrier concentrations at the edges of the depletion region and reflect qualitativelythe decay of (injected or depleted) minority