Semiconductor devices: p-n junctions

1. A GaAs wafer has a variation in electron concentration across the wafer. The

electron concentration drops from 1018 cm3 to 1016 cm³ across a distance of 2

um. The electron mobility of GaAs at room temperature is 8500 cm²V-¹s1.

a) Using the Einstein relation, calculate the diffusion constant for GaAs at

room temperature.

b) What is the current density due to electron diffusion in the GaAs wafer?