Electroreflectance of p-type GaAs

The electroreflectance spectra of p-type GaAs in photon energies from 1.3 to 3.5 eV have been investigated at temperatures from 300° down to 25°K. Measurements of electroreflectance have been performed by the method using the interface potential of GaAs-SnO₂ heterojunction. Both signals of an exciton and the fundamental edge have been separated in the low temperature spectra, and an additional structure which may be associated with a localized state has been also observed below the fundamental edge. The similar structures with weak intensity appear near the spin-orbit split off edge. The line shapes of electroreflectance spectra which are related to Λ₃−Λ₁ transition and its spin-orbit split off edges are explained by the mixed electro-optical spectra of M₁() and M₁() type critical points including the effect of thermal broadening. A method of estimating the thermal broadening factor from the temperature dependences of the electroreflectance spectra associated with Λ₃−Λ₁ transition edge is also presented.