Study of AlGaAs/GaAs quantum wells overgrown on in situ Cl2-etched GaAs substrates

We have studied the properties of in situ Cl2-etched GaAs surfaces and overgrown quantum well (QW) structures as a function of the etching temperature. From reflection high-energy electron diffraction, atomic force microscopy, and Auger electron spectroscopy analysis on Cl2-etched surfaces we found that low etching temperatures (∼50 °C) results in Ga-rich rough surfaces, because at these temperatures the desorption rate of Ga chlorides is much slower than that for As chlorides. At high etching temperatures (∼200 °C) both Ga and As chlorides can be removed, resulting in a more stoichiometric etching which yields a smooth GaAs surface. The optical properties of QW structures overgrown on in situ etched surfaces were compared to those of an ex situ processed sample. For the ex situ processed sample we found degraded photoluminescence (PL) characteristics and a high amount of impurities. The PL properties improved, and the amount of impurities sharply decreased in the in situ sample Cl2 etched at 200 °C. Phot...

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