NONPARABOLICITY OF THE CONDUCTION-BAND IN GAAS

The technique of resonant Raman scattering is used in a magnetic field to determine interband magneto-optical transitions in GaAs(001) from enhancements of the 1-LO- and 2-LO-phonon intensities due to resonances with Landau levels. The experiments were performed far above the E0 fundamental gap, where corrections due to Coulomb effects can be neglected. We observed incoming, outgoing, and intermediate resonances involving only heavy-mass valence levels. These levels can be described rather accurately by solving an 8×8 kp matrix with 30 Pidgeon-Brown blocks, and therefore, the observed nonlinearities in the fan plots of laser energy Latin small letter h with strokel versus magnetic field B for transitions with Landau quantum numbers n can be attributed to the nonparabolicity of the 6c conduction band of GaAs. A simple formula for the bulk 6c dispersion is deduced from a two-band model with only one parameter to fit the fan plots for different scattering configurations and types of resonances. This yields an experimental determination of the conduction-band dispersion and effective mass in the region from 100 meV up to about 300 meV above the E0 fundamental gap. Our results compare favorably with 16×16 kp and pseudopotential calculations. © 1990 The American Physical Society.