Field-induced carrier transport and optical phonon instability in semiconductor nanostructures

Transient electron and hole distributions as well as longitudinal optical phonons in semiconductor nanostructures are studied under the application of an electric field by picosecond/sub-picosecond time-resolved Raman spectroscopy. The experimental results of carrier transport for Gallium Arsenide, Indium Gallium Arsenide, Aluminum Gallium Arsenide, and Indium Nitride are presented and discussed. Electron and hole velocity overshoots have been observed. The experimental results have been compared with ensemble Monte Carlo simulations and good agreement has been obtained. Optical phonon instability in a Gallium Arsenide p-i-n nanostructure is observed. It is demonstrated that optical phonon amplification occurs whenever electron drift velocity is larger than the phase velocity of the optical phonon. These experimental results are also in good agreement with theoretical calculations based on the random-phase-approximation.