Absorption Edge in Degenerate <i>p</i>-Type GaAs

Abstract

Infrared absorption for p-type degenerate GaAs is studied at room temperature for various hole concentrations. At high absorption coefficients, a Burstein-like shift is observed for samples doped above 1019/cm3; this shift is interpreted as a decrease in the valence band electron population. A direct transition analysis was made on 1017/cm3 material, yielding an energy gap of 1.39±0.02 ev. The free carrier absorption was extrapolated to shorter wavelengths and subtracted from the data. The resulting absorption edges extend to energies beyond the fundamental edge and reveal the presence of an added absorption mechanism.