We discove the decrement,comparing the Electroreflectance spectroscopy of theforward biased voltage is 0.5V after the photon energy is 1.8eV.We discuss the case from Asymptotic form and the sample.

The electroreflectance (ER) of surface-intrinsic-n+ type doped GaAs has exhibited many Franz-Keldysh oscillations to enable the application of fast Fourier transform to separate the heavy and light-hole transitions. In this work, we can get the dependence of surface electric field on external biased voltage from analyzing the Franz- Keldysh oscillations and the way of fast Fourier transform on condition that weakly modulated field, further more we can get the dependence of effective reduced mass on changed photon energy.