PHOTOREFLECTANCE AND PHOTOLUMINESCENCE CHARACTERIZATION OF GAAS QUANTUM-WELLS GROWN BY MOLECULAR-BEAM EPITAXY ON FLAT AND MISORIENTED SUBSTRATES

Photoreflectance (PR) and photoluminescence (PL) spectroscopies were e mployed in the characterization of molecular beam epitaxially grown Ga As/AlGaAs quantum wells grown on nominally flat (100) oriented and (10 0) misoriented GaAs substrates. Four quantum wells with nominal thickn ess of 100, 75, 50 and 25 Angstrom were grown employing different temp eratures between 600 and 650 degrees C and growth rates of 0.5 and 1 m u m/h. Room temperature PR allowed us to obtain the actual aluminum co mposition (x = 0.27), and obtain the magnitude of the interfacial elec tric field (similar to 10(6) V/cm). An evaluation of the abruptness of the quantum well interfaces was done from the analysis of PL and PR s pectra in terms of the finite quantum well theory. The overall results clearly indicated that the step-flow growth mode on the misoriented s ubstrate produced superior crystallinity of the heterostructures. In t he case of growth on flat substrates higher temperatures and slower gr owth rates gave broader interfaces and thinner wells.