Inequivalence of normal and inverted interfaces of molecular-beam epitaxy grown AlGaAs/GaAs quantum wells

Normal and inverted interfaces of GaAs/AlGaAs heterostructures are studied by comparing the luminescence of quantum wells (QWs) grown by molecular-beam epitaxy with a 10–300 s growth interruption either at one or both of the interfaces. The influence of growth interruption time on the incorporation of shallow impurities and traps and on the variation of the interface structure is investigated. GaAs surfaces become appreciably smoother with increasing interruption time, and increasing incorporation of shallow impurities, but no incorporation of traps at the growth surface is observed. At AlGaAs surfaces, the concentration of traps strongly increases with growth interruption time, but the surface does not become smoother. Additionally strong accumulation of shallow impurities at the inverted GaAs-on-AlGaAs interface is directly visualized.