Pressure dependence of optical absorption in GaAs at 77 K

Optical absorption measurements on GaAs have been made as a function of pressure up to 100 kbar at 77 K. A low-energy tail in the absorption spectrum is observed above 40 kbar, which is attributed to the Gamma -X indirect optical transitions. This leads to a determination of the pressure dependence of the indirect band gap. The effects of high doping on the absorption spectra are also investigated.