Field-induced nonequilibrium carrier distributions in GaAs probed by electronic Raman scattering

Inelastic light scattering is used to probe nonequilibrium carrier distributions in active GaAs devices. Unlike many photoexcited nonequilibrium studies, this work examines carrier distributions in electrically biased ${\mathit{n}}^{+}$-${\mathit{n}}^{\mathrm{-}}$-${\mathit{n}}^{+}$ GaAs devices. Using a laser with photon energy lower than, but within 100 meV of, the direct band gap, single-particle and collective scattering events were observed in an effort to determine the hot-electron distribution function. Results are presented for various bias conditions. Due to the number and complexity of scattering mechanisms that contribute to the observed spectra, the effects of the applied field were more accurately analyzed by examining the differences between the equilibrium and nonequilibrium spectra. The carrier temperature and average drift velocity as a function of field strength were determined by fitting a theoretical model of the scattering cross section to the observed spectra.