Faculty Publications

Title

Study of deposition dependent characteristics of gold on n-GaAs by photoreflectance spectroscopy

Document Type

Article

Journal/Book/Conference Title

Journal of Applied Physics

Volume

81

Issue

2

First Page

910

Last Page

916

Abstract

We used the noncontact electric field modulation technique of photoreflectance to study the effect of gold on GaAs grown by two different metalization methods. A semitransparent 7 nm gold overlayer was grown on low doped n-GaAs (2×1016 cm-3) using metalization by evaporation and by sputtering. Our experimental results indicate that the photoreflectance lineshape depends on the metalization method in a characteristic way. We present evidence of a previously unreported modulation mechanism in photoreflectance. We employed simulation of photoreflectance lineshape based on a multilayer model to reproduce characteristic features of experimental lineshapes. For sputtered Au/GaAs samples the best simulated lineshape was obtained through an unusual modulation, which is based on a strongly pined surface electric field. This produced a lineshape somewhat similar to a third derivative functional form with severely suppressed Franz-Keldysh oscillations (FKO). Simulation with the same set of parameters and a parallel field modulation restored FKO and reproduced the experimental lineshape of the evaporated Au/GaAs. The parallel field modulation spontaneously reproduced the below-band-gap feature, which is often observed in electromodulation spectroscopy. We believe the change in FKO is correlated with the density of interface states as they influence the extent of Fermi-level pinning. © 1997 American Institute of Physics.

Original Publication Date

1-15-1997

DOI of published version

10.1063/1.364175

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