Determination of intervalley scattering rates in GaAs by subpicosecond luminescence spectroscopy

We report a slow rise of luminescence in GaAs following subpicosecond photoexcitation and show that it results from a slow return of electrons from the L to the valley. By fitting our data with an ensemble Monte Carlo calculation, we determine the -L deformation potential to be (6. 51. 5) 10^8 eV/cm. We show that the electrons returning to the valley act as a source of heating for the photoexcited plasma. We further show the importance of electron-electron scattering and inadequacy of a simple phonon-cascade model, even at a density as low as 510^16 cm^-3.