Electronic Raman scattering from valley-orbit transitions in uniaxially stressed Ge(As)

Electronic Raman scattering from the stress-split valley-orbit transition in Ge(As) is reported for uniaxial stress along both the [111] and [110] directions. Each of the observed spectral components is shown to obey the group theoretically derived selection rules. A detailed quantitative comparison of the experimental positions of the spectral components is made with the theoretical predictions of Price. Raman shifts associated with $1s\left\{A_1\right\}\to 1s\left({\Gamma }_j\right)$ transitions (${\Gamma }_i\ne A_1$) can be accurately calculated using this theory. A discrepancy between theoretical predictions and the experimental results for the $1s\left\{A_1\right\}\to 1s\left(A_1\right)$ transitions is attributed to stress-induced hybridization between the $1s\left(A_1\right)$ and $2s\left\{A_1\right\}$ states. After including hybridization effects the agreement between theoretical predictions and the experimental spectral positions is excellent. The shear deformation potential, ${\Xi }_u$, for the $1s$ manifold of impurity states was determined to be 17.8 ± 0.5 eV. The experimentally determined intensities of the observed electronic Raman lines are compared with theoretical calculations for the stress-dependent Raman cross section of the valley-orbit transition.