Potential fluctuations in high-purity n-type III-V semiconductors

Abstract

We investigate the effects of fluctuations in the Coulomb potential due to charged impurities in high-purity n-type III-V semiconductors at low temperatures. Assuming that charged donors and acceptors are randomly distributed at high temperatures, we conclude that the donors are selectively filled at low temperatures leaving nonrandom distributions of charged and filled donors. The potential fluctuations from these distributions can approximately account for a number of experimental observations on low-temperature high-purity GaAs including the apparent decrease of donor binding energy with increasing impurity concentration observed in Hall measurements, the sharpness and temperature dependence of the ls-2p transition along with the diffuse ls-conduction band edge observed in photoconductivity experiments, and the fact that experimentally observed photoconductivity line shapes are narrower than those previously predicted.