Raman spectroscopic and Hall effect analysis of the free electron concentration in GaAs with ultrahigh silicon doping.

Heavily silicon-doped GaAs grown by molecular beam epitaxy has been studied by combined coupled plasmon-phonon mode Raman spectroscopy and Hall effect measurements. Free electron concentrations up to 2x10high19 cmhighminus3 have been achieved with the dopant atoms being incorporated dominantly on Ga sites (bigger than 90%) as measured by local vibrational mode Raman spectroscopy. To extract quantitative information from the plasmon-phonon Raman spectra, these spectra have been fitted using the temperature-dependent Lindhard-Mermin dielectric function including the nonparabolicity of the conduction band and wave vector nonconservation due to the absorption of the incident and scattered light. The excellent agreement found between Hall effect and Raman measurements demonstrates that consistent data on dopant incorporation and activation can be obtained, if band structure effects are accounted for appropriately in the analysis of the Raman spectra.