Abstract
We report room-temperature Raman scattering studies of nominally undoped (100) GaAs1 Bi-x(x) epitaxial layers exhibiting Bi-induced (p-type) longitudinal-optical-plasmon-coupled (LOPC) modes for 0.018 <= x <= 0.048. Redshifts in the GaAs-like optical modes due to alloying are evaluated and are paralleled by strong damping of the LOPC. The relative integrated Raman intensities of LO(Gamma) and LOPC A(LO)/A(LOPC) are characteristic of heavily doped p-GaAs, with a remarkable near total screening of the LO(G) phonon (A(LO)/A(LOPC) -> 0) for larger Bi concentrations. A method of spectral analysis is set out which yields estimates of hole concentrations in excess of 5 x 10(17) cm(-3) and correlates with the Bi molar fraction. These findings are in general agreement with recent electrical transport measurements performed on the alloy, and while the absolute size of the hole concentrations differ, likely origins for the discrepancy are discussed. We conclude that the damped LO-phonon-hole-plasmon coupling phenomena plays a dominant role in Raman scattering from unpassivated nominally undoped GaAsBi. (C) 2014 Optical Society of America