Plasmon Raman scattering and photoluminescence of heavily dopedn-type InP near the Γ-X crossover

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Abstract
We have measured Raman scattering by coupled longitudinal-optic-phonon-plasmon modes and photoluminescence in heavily doped n-type InP under hydrostatic pressure and at low temperatures. The combination of both methods allows us to determine the pressure dependence of the carrier density and the enhancement of the effective electron mass of the Γ conduction-band minimum due to nonparabolicity. Above 10.3 GPa a striking change in the frequency of the upper coupled mode is observed, which is attributed to the transfer of electrons from the Γ minimum to X-related states. From the onset pressure for the Γ to X electron transfer we determine the pressure coefficient of the indirect Γ-X gap [-17(3) meV/GPa] and a pressure of 11.2 ± 0.4 GPa for the Γ-X conduction-band crossover in undoped InP. © 1996 The American Physical Society.