Recombination at GaAs surfaces and GaAs/AlGaAs interfaces probed by in situ photoluminescence

We use in situ photoluminescence (PL) to investigate recombination at (100)GaAs surfaces and GaAs/AlGaAs interfaces in a controlled crystal growth environment. PL was monitored for different GaAs surface reconstructions, after surface chemical modification, and during early stages of AlGaAs heteroepitaxy. Depositing ∼1 ML of Se to form a (2×1) surface increased the GaAs PL intensity 200 times. Surprisingly, it required 6 ML (15 Å) of heteroepitaxial AlGaAs to achieve the same degree of surface passivation. We invoke lateral variations in interfacial AlGaAs composition to explain these results.