OBSERVATION OF HOT-ELECTRON RELAXATION IN GAAS ALGAAS MULTIPLE-QUANTUM WELLS BY EXCITATION SPECTROSCOPY/

Hot electron relaxation in GaAs/AlGaAs multiple quantum well (MQW) str ucture was studied with the use of photoluminescence excitation (PLE) spectroscopy. Oscillation due to the emission of confined longitudinal optical (LO) GaAs phonons, by photoexcited electrons were observed in the (6 K) excitation spectra. The period of the oscillation is differ ent from that observed in bulk GaAs. The calculation from a four-band Kane model, describing the mixing of heavy-and light-hole bands at wav e vector away from k=0, was used to interpret the difference of oscill ation features between the GaAs/AlGaAs MQW structure and bulk GaAs. Th e recorded PLE spectrum and calculated results show that photoexcited electrons can directly cascade downwards to the exciton energy state b y LO phonon emissions. (C) 1997 American Vacuum Society.