S. Ernst et al., PLASMON RAMAN-SCATTERING AND PHOTOLUMINESCENCE OF HEAVILY-DOPED N-TYPE INP NEAR THE GAMMA-X CROSSOVER, Physical review. B, Condensed matter, 53(3), 1996, pp. 1287-1293
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 Gam
ma conduction-band minimum due to nonparabolicity. Above 10.3 GPa a st
riking change in the frequency of the upper coupled mode is observed,
which is attributed to the transfer of electrons from the Gamma minimu
m to X-related states. From the onset pressure for the Gamma to X elec
tron transfer we determine the pressure coefficient of the indirect Ga
mma-X gap [-17(3) meV/GPa] and a pressure of 11.2 +/- 0.4 GPa for the
Gamma-X conduction-band crossover in undoped InP.