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 $E_0-E_0+{\Delta }_0$ and $E_1-E_1+{\Delta }_1$ 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 $E_0-E_0+{\Delta }_0$ 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°K as well as 77°K in the $E_1-E_1+{\Delta }_1$ 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°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 $E_1-E_1+{\Delta }_1$ 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.