Unequal electron and hole impact ionization coefficients in GaAs

Abstract

GaAs Schottky barrier avalanche photodiodes have been fabricated in which it is possible to achieve nearly pure hole and pure electron injection in the same device. Measurements of the multiplication characteristics of these devices show that the ionization coefficients of electrons (α) and holes (β) are not equal and that β>α. This result is in agreement with the variation of multiplication with bias voltage at different wavelengths observed for standard GaAs Schottky barrier diodes but contrary to the generally accepted belief that α=β.