Stress effects on excitons bound to shallow acceptors in GaAs

Abstract

We have performed stress-dependent photoluminescence measurements on excitons bound to neutral shallow acceptors (${A}^{0}X$) in GaAs. From their temperature and stress variation three lines (at zero stress) are proved to be due to the decay of (${A}^{0}X$) with the $J=\frac{5}{2}$ state lowest. When low uniaxial stress (0-2 ${\mathrm{kg}\mathrm{mm}}^{\ensuremath{-}2}$) is applied these three lines split into 7 or 8 components, although at high stress only one line remains with a stress shift equal to that for the conduction band to acceptor recombination. A theoretical interpretation based on a bonding two-hole state analogous to the ${\mathrm{H}}_{2}$ molecule is found to agree well with the data when the effects of a weak crystal field are included. Small deviations between this theory and experiment are presumed to indicate the importance of the antibonding two-hole functions in the (${A}^{0}X$) wave function.