Time-resolved photoluminescence of two-dimensional hot electrons in GaAs-AlGaAs heterostructures.

We have studied the picosecond time dependence of luminescence from a two-dimensional electron system following absorption of an ultra-short light pulse. From our measurements we determine the temporal evolution of the electron temperature, finding that the cooling of hot electrons is suppressed by a factor 60 below that predicted on a three-dimensional, nondegenerate electron model. Additionally, we determine the electron-hole radiative lifetime and invoke a hole trap to explain shortened luminescence lifetimes at low carrier densities.