MULTISTEP FORMATION AND LATERAL VARIATION IN THE IN COMPOSITION IN INGAAS LAYERS GROWN BY METALORGANIC VAPOR-PHASE EPITAXY ON (001)VICINAL GAAS SUBSTRATES

In this paper, we investigate the substrate misorientation effect on In0.2Ga0.8As/GaAs strained quantum wells grown on vicinal GaAs substrates by metalorganic vapor phase epitaxy (MOVPE). Using cross-sectional transmission electron microscopy (TEM), stepbunching in an InGaAs layer is observed. In addition, based on energy-dispersive X-ray (EDX) analysis, we report for the first time lateral variations in the In composition in an InGaAs layer grown on a vicinal substrate. It is found that this variation in In composition and variations in the thickness cause photoluminescence (PL) spectrum broadening. The dependence of PL properties on the growth conditions and on surface misorientation direction is also examined. Experimentals results are explained by discussing the diffusion length of Group III atoms and their tendency to attach to step sites. TEM analysis confirms that the critical layer thickness of an InGaAs layer decreases on a vicinal substrate due to the formation of stepbunches.