Determination of built-in field by applying fast Fourier transform to the photoreflectance of surface-intrinsic n(+)-type doped GaAs

Photoreflectance spectroscopy of surface-intrinsic n(+)-doped (s-i-n(+)) Ga As has been measured at various power densities (P-pu) of a pump beam. Many Franz-Keldysh oscillations (FKOs) were observed above the band-gap energy, which will enable the electric-field strength (F) to be determined from th e periods of the FKOs. Field F thus obtained is subject to photovoltaic eff ects. In order to reduce the photovoltaic effects from the pump beam, P-pu was kept below 10 mu W/cm(2) in the previous experiments. Here, we demonstr ate that the built-in field can be determined at a larger P-pu by using fas t Fourier transform techniques. (C) 1999 American Institute of Physics. [S0 003-6951(99)02803-X].