Piezo-Electroreflectance in Ge, GaAs, and Si

We have investigated the effect of static uniaxial compression along the 001, 110, and 111 directions on the E₀, E₀+₀, E₁, and E₁+₁ electroreflectance peaks of Ge and GaAs, and the {E₀}^' electroreflectance peaks of Si. From the stress-induced splittings and shifts of the E₀, E₀+₀ peaks of Ge and GaAs, the hydrostatic and shear deformation potentials of the k=0 valence-band maximum have been determined. We have also observed a nonlinear stress dependence of the energies of these peaks, which is caused by the stress-induced coupling between the upper stress-split valence band and the spin-orbit split band. A theory for the stress-induced variations in intensity caused by this interaction will be presented and compared with the experimental results. The hydrostatic and shear deformation potentials of the ₁-conduction and ₃-valence bands of Ge and GaAs have been determined from the stress dependence of the E₁ and E₁+₁ peaks of these materials. We have attributed the observed stress-induced changes in intensity of these peaks to the intraband splitting of the ₃-orbital valence bands. The experimental results are compared with our theoretical calculations. The stress dependence of the {E₀}^' electroreflectance peaks of Si for 001 stress seems to indicate that 100 critical points are responsible for this structure. However, we have also observed large polarization-dependent intensity changes for 111 stress, which we have not been able to explain on the basis of the above assignment.