Field-inhomogeneity-induced lineshape rotation observed in room-temperature electroreflectance spectra of GaAs

In the presence of a DC bias the influence of electric field inhomogeneity in the space charge region of doped GaAs on electroreflectance spectra has been studied by model calculations which are compared with experimental results. Field inhomogeneity effects are shown to modify the spectra near the gap in a characteristic manner. The predictions of the theory concerning lineshape 'rotation' with a DC bias, estimation of the gap energy and doping dependence f the spectra are confirmed by measurements on a set of doped GaAs samples. It is shown that the field inhomogeneity and not the effect of excitons is mainly responsible for the observed lineshape 'rotation' at room temperature. However, owing to the same bias dependence of both mechanisms there is no simple way of distinguishing between them.

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