High-temperature surface cleaning of AlGaAs without As flux for MBE regrowth

AlGaAs surfaces were cleaned by high-temperature heat treatment without As flux in a preparation chamber for regrowth of active layers by molecular beam epitaxy (MBE). Reflection high-energy electron diffraction from the cleaned AlGaAs surface showed a spotty pattern, but surface roughness observed by an atomic force microscope was smaller than the surface of cleaned GaAs. Auger electron spectroscopy showed that a cleaned surface was covered by Al, As and O-2. Surface sublimation measured by quadrupole mass spectroscopy during the heat treatment decreased drastically with increasing alloy composition x, suggesting that the cleaned surface consisted of AlAs or its oxide. Quantum well (QW) structures were grown on the cleaned surfaces and photoluminescence (PL) spectra were measured. Well-defined PL peaks corresponding to stacked single QWs (SQWs) with 500 nm thick buffer layer were obtained at 300 K, which were in contrast to the SQWs grown on the surface cleaned by the conventional method. The PL intensity was influenced strongly by the thickness of the buffer layer when it was thinner than 300 nm. GaAs passivation of the AlGaAs surface was effective for obtaining intense PL spectrum from the regrown SQWs.