Abstract
Photomodulation Raman spectroscopy (PM-RS) was employed to investigate the interfacial properties of Au: n-type GaAs interfaces, using the forbidden longitudinal optical (LO) phonon scattering as a probe. In PM-RS, the photomodulating pump beam (PB) is incident on the sample while the Raman measurements are in progress; hence, PM-RS can be viewed as a pump-probe technique. The photogenerated carriers partly neutralize the surface charges, which decreases the interfacial field and consequently the intensity of forbidden LO scattering. Two molecular beam epitaxy (MBE) junctions of 80 angstrom Au on n-type GaAs (001) substrate with two different doping densities were used. The total surface charge density and change in the band bending were obtained as a function of the PB intensity considering a constant depletion electric field for the lower doped sample. Furthermore, the interfacial minority carrier trap lifetime was determined through dynamical measurements of the PM-RS intensity. Copyright (C) 2010 John Wiley & Sons, Ltd.