Growth optimization and optical properties of GaAs-(Ga,Al)As quantum well structures on UV-ozone prepared nominal (111)B GaAs surfaces

GaAs and (Ga,Al)As---GaAs quantum well (QW) structures have been grown by molecular beam epitaxy on nominal (111)B oriented GaAs substrates. The substrate preparation technique involving UV-ozone oxidation was observed to lead to a rough surface after oxide desorption. Mirror-like layer surfaces have nevertheless been achieved by applying a careful procedure during the first stages of growth in order to recover surface flatness. New evidence of planarization is presented, based on the frequency analysis of reflection high-energy electron diffraction (RHEED) intensity oscillations during growth. QWs grown at a moderate substrate temperature (about 610°C) have been obtained with sharp excitonic transitions whose photoluminescence (PL) emission linewidths are comparable to those obtained on misoriented (111)B substrates. In contrast, the use of higher substrate temperatures was found to provide rougher interfaces due to GaAs sublimation during growth interruption at each interface, as revealed by continuous wave and time-resolved PL measurements.