Femtosecond hole relaxation inn-type modulation-doped quantum wells

We present a study of femtosecond hole-relaxation dynamics in n-modulation-doped GaAs/${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum wells at low temperatures and low photoexcitation density. We conclude that holes are nonthermal for approximately the first 800 fs and determine the hole-electron energy loss rates by comparing experimental results with Monte Carlo simulations. These results represent a definitive study of hole scattering and relaxation processes in a semiconductor.