Thermalization of hot electrons in quantum wells

We present a new photoluminescence technique for studying hot electron relaxation in quantum wells. Two lasers are used to measure the density of photoexcited electrons at energies well above the thermalized distribution. The method has been used to determine the relaxation rate for hot electrons in a GaAs/Al _1-xGa _xAs multi-quantum well structure with an electron density of 2.5×10 ¹¹/cm ². Electrons appear to “bottleneck” in a subband, thermalizing about 10 times more slowly (0.03 eV/ps) at the bottom of the subband than higher up.