Electron velocity overshoot in GaAs studied by subpicosecond Raman spectroscopy: carrier density dependence

摘要

Abstract: Electron transient transport in a GaAs-based p-i-n nanostructure under the application of an electric field has been studied by transient Raman spectroscopy at T $EQ 80 K. The non-equilibrium electron distribution function and electron drift velocity were measured at an applied electric field intensity of E $EQ 25 kV/cm and for various injected electron-hole pair densities ranging from 10$+17$/ cm$+$MIN@3$/ to 10$+19$/ cm$+$MIN@3$/. Our experimental results show that, the electron distribution is very much out of equilibrium for n $CNGR 10$+17$/ cm$+$MIN@3$/; however, as the electron-hole pair density increase the electron distribution function approaches that of the equilibrium case, in particular, as the carrier density increases to n $CNGR 10$+19$/ cm$+$MIN@3$/, electron distribution becomes very much in equilibrium and electron drift velocity becomes almost zero. These results have been explained by the effects of momentum randomization and screening of effective electron field by the injected electron-hole pairs.!16