Optical Absorption inp-Type Gallium Arsenide

In $p$-type gallium arsenide, a number of absorption bands have been observed on the low-energy side of the intrinsic absorption edge. The absorption spectrum has a distinct peak at 0.42 ev, a partially resolved peak at 0.31 ev and the beginning of a strong absorption band setting in at 0.25 ev. The main features of the spectra can be explained in terms of hole-transitions between different branches of the valence band of gallium arsenide. The transitions between light- and heavy-hole bands and a band split off by spin-orbit splitting are identified. The spin-orbit splitting is ∼0.34 ev.