It is known that electroreflectance 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. However, each peak still contains two components, which belong to F+δF/2 and F-δF/2, respectively, where F is the electric-field strength in the undoped layer and δF is the modulating field of applied ac voltage (V_(ac)). In order to resolve the heavy- and light-hole transitions, δF was kept much smaller than F in the previous works. In this work, we have used a larger V_(ac) and, hence, a larger δF, to further separate the peaks. The peaks can be divided into two groups which belong to F+δF/2 and F-δF/2, respectively. The peak belonging to the heavy-hole transition and F-δF/2 can be singled out to compare with the Airy function theory.
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