In-situ monitoring, structural, and optical properties of ultrathin GaSb/GaAs quantum wells grown by OMVPE

We present a study of the growth of strained ultrathin GaSb quantum well (Q W) layers in a GaAs host crystal by organometallic vapor phase epitaxy (OMV PE). We report surface anisotropy features observed by reflectance differen ce spectroscopy (RDS) during exposure of the GaAs (001) surface to trimethy lantimony (TMSb) and during subsequent growth interruption. We demonstrate the formation of a floating layer of Sb during growth of GaAs over GaSb qua ntum well layers. The periodic nature of the RDS signal during growth of mu ltiple quantum well (MQW) structures allows us to construct time-resolved R DS spectra, detailing the evolution of the surface anisotropy. We show how x-ray diffraction (XRD) data may be used to determine the graded compositio nal profile resulting from Sb segregation at the GaAs/GaSb interface. Photo luminescence (PL) spectra at 2 K from MQW structures exhibit two peaks belo w the GaAs bandgap. The lower-energy peak, which we attribute to a type-II transition at the GaSb/GaAs interface, shifts logarithmically with excitati on power density. The higher energy peak shows no shift with excitation pow er, and is attributed to a transition occurring within the graded barrier l ayers.