Effects of uniaxial stress on the electroreflectance spectrum of Ge and GaAs

Abstract

We have investigated the effects of static uniaxial compression along [001] and [111] on the Schottky-barrier electroreflectance spectrum of the ${E}_{0}\ensuremath{-}{E}_{0}+{\ensuremath{\Delta}}_{0}$ and ${E}_{1}\ensuremath{-}{E}_{1}+{\ensuremath{\Delta}}_{1}$ transitions in Ge and GaAs. From the stress-induced splittings and shifts of these optical structures we have obtained deformation potentials, spin-exchange parameters and reduced interband masses. For the ${E}_{0}\ensuremath{-}{E}_{0}+{\ensuremath{\Delta}}_{0}$ transitions orbital (${b}_{1}$ and ${d}_{1}$), spin-dependent (${b}_{2}$ and ${d}_{2}$), and hydrostatic deformation potentials have been determined. In GaAs these are the first measurements reported for ${b}_{2}$ and ${d}_{2}$. The other parameters were found to be in good agreement with previous works. Interband reduced masses for the ${E}_{0}$ transition in Ge were determined at high stresses, in which case the degenerate valence band is split and the constant-energy surfaces are parabolic. Conclusive evidence for the existence of the electron-hole Coulomb interaction at 300\ifmmode^\circ\else\textdegree\fi{}K as well as 77\ifmmode^\circ\else\textdegree\fi{}K in the ${E}_{1}\ensuremath{-}{E}_{1}+{\ensuremath{\Delta}}_{1}$ transitions has been obtained from the polarization-dependent stress-induced splittings for [001] stress. The observed splitting is not explained by one-electron theory but is accounted for by including the electron-hole exchange interaction. By including exciton effects at 300\ifmmode^\circ\else\textdegree\fi{}K the systematic discrepancy between theory and experiment for the intensity and line shape of this structure should be resolved. In addition, deformation potentials due to shear (${D}_{1}^{5}$), hydrostatic (${D}_{1}^{1}$), and intraband (${D}_{3}^{3}$) effects were determined for the ${E}_{1}\ensuremath{-}{E}_{1}+{\ensuremath{\Delta}}_{1}$ transitions. The values obtained for ${D}_{1}^{5}$ in GaAs and Ge were found to be almost a factor of 2 larger than those previously reported. The reason for this is believed to be the higher resolution of the present experiments. Other parameters agree with prior works.