EFFECT OF PRESSURE ON THE LOW-TEMPERATURE EXCITON ABSORPTION IN GAAS

We have measured low-temperature exciton optical-absorption spectra at the lowest direct band edge (E0) of GaAs as a function of pressure up to 9 GPa. Spectra are analyzed in terms of the Elliott model by taking into account the broadening of the exciton line. In this way, we determine the dependence on pressure of the E0 gap, the exciton binding energy scrR, and exciton linewidth at different temperatures. The pressure coefficient of the E0 fundamental gap [107(4) meV/GPa] is found to be independent of temperature. The exciton binding energy increases with pressure at a rate of d lnscrR/dP=0.083(3) GPa-1. The exciton lifetime becomes smaller for pressures above the crossover between - and X-point conduction-band minima (P>4.2 GPa), a fact which is attributed to phonon-assisted intervalley scattering. From the pressure dependence of the exciton linewidth we determine an accurate value for the intervalley deformation-potential constant DX=4.8(3) eV/. © 1990 The American Physical Society.