The preparation of InAs 1− xSb x alloys and strained-layer superlattices by MOCVD

Abstract

Epitaxial layers of InAs 1− x Sb x (0.0⩽ x⩽1.0) have been prepared by MOCVD in a vertical, atmospheric pressure quartz reaction chamber. Trimethylindium (TMI), trimethylantimony (TMSb), and arsine in H 2 were used as the source materials. The best surface morphologies and sharpest X-ray patterns were obtained for a growth temperature of 475°C, a TMI/(TMSb+AsH 3) molar ratio equal to 1.00, and a growth rate of less than 1.0μ/h. The growth efficiencies of InSb and InAs 1− x Sb x at 475°C are 3500 and 2000 μ/mol In, respectively. The growth rates were found to be thermally activated. The solid composition of the ternary can be predicted by a thermodynamic model from the starting partial pressures of the reactants. Strained-layer superlattices (SLS's) of the type InAs 1− x Sb x have been prepared by a purge/growth technique. The SLS's were characterized by optical microscopy, X-ray diffraction and transmission electron microscopy. The presence of residual tension between the superlattice and the buffer layer or the buffer layer and the substrate can result in the formation of microcracks and misfit dislocations. Residual defects on the substrate also result in the formation of dislocations. These dislocations can be minimized by growing the superlattices on top of a step graded buffer layer which eliminates the microcracks.