Effect of pressure on the low-temperature exciton absorption in GaAs

Abstract

We have measured low-temperature exciton optical-absorption spectra at the lowest direct band edge (${\mathit{E}}_0$) 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 ${\mathit{E}}_0$ gap, the exciton binding energy scrR, and exciton linewidth at different temperatures. The pressure coefficient of the ${\mathit{E}}_0$ 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) ${\mathrm{GPa}}^{\mathrm{-}1}$. The exciton lifetime becomes smaller for pressures above the crossover between Γ- 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 ${\mathit{D}}_{\mathrm{\Gamma }\mathit{X}}$=4.8(3) eV/Å.