Femtosecond relaxation of photoexcited holes in bulk gallium arsenide

The relaxation to the top of the valence band of nonequilibrium photoexcited holes in n-type doped bulk gallium arsenide at 77 K is selectively measured by a femtosecond luminescence up-conversion technique. In the low-excitation regime, hole decay times between 560 and 330 fs are observed for fully-ionized-donor concentrations in the range 6×${10}^{17}$ to 2.4×${10}^{18}$ ${\mathrm{cm}}^{\mathrm{-}3}$. The theoretical treatment of weakly photoexcited n-type GaAs displays certain simplifications when compared with earlier work, as both the lattice and the electron bath are in thermodynamic equilibrium, and the results of a simulation invoking hole–LO-phonon and hole-electron interactions give good agreement with experiment.