Analysis of Raman Spectra from Heavily Doped<i>p</i>-GaAs

Abstract

A theory of Raman scattering by both coupled LO phonon-plasmon (LO-PL) modes and surface “unscreened” LO phonons in a doped semiconductor is presented with a simple two-layer (surface depletion layer-bulk substrate) model. Effects of the optical penetration depth and the depletion layer thickness on the line shape are examined. The theory is applied to an analysis of Raman spectra from a (100) surface of p -GaAs, and reproduces experimental profiles very well. An analysis suggests that the observed broad band near the transverse optical phonon frequency is ascribed to the lower branch of the coupled LO-PL modes.