Evaluation of modulating field of photoreflectance of surface-intrinsic-n(+) type doped GaAs by using photoinduced voltage

Abstract

Photoreflectance (PR) of surface-intrinsic-n(+) type doped GaAs has been measured for various power densities of pump laser. The spectra exhibited many Franz-Keldysh oscillations, whereby the strength of electric field F in the undoped layer can be determined. The thus obtained Fs are subject to photovoltaic effect and are less than built-in field F-bi. In the previous work we have obtained the relation Fapproximate toF(bi)-deltaF/2 when deltaF<F-bi by using electroreflectance to simulate PR, where deltaF is the modulating field of the pump beam. In this work a method was devised to evaluate deltaF by using photoinduced voltages V-s and, hence, the relation can be verified by PR itself. The deltaFs obtained by V-s are also consistent with those of using imaginary part of fast Fourier transform of PR spectra. (C) 2002 American Institute of Physics.