InAs1-ySby virtual substrates grown by MOCVD for long wave infrared detectors

Compositionally-graded InAs1-ySby metamorphic buffers, grown on GaSb wafers via metal organic chemical vapor deposition and designed to serve as virtual substrates for InAs0.6Sb0.4 long wave infrared detectors, were investigated for their potential to provide low residual threading dislocation densities. Structural properties of a range of step-graded buffer designs, including surface morphology, strain relaxation, and residual threading dislocation density were investigated as a function of substrate orientation, initial layer composition (lattice mismatch), grading rate, and compositional step size and thickness, and used to guide optimization of the metamorphic buffer structure. A minimum threading dislocation density of 2 x 10(6) cm(-2) within the InAs0.6Sb0.4 terminal layer was achieved through use of a 7-layer buffer design with a strain grading rate of - 0.78% mu m(-1), with potential for further reduction by continued optimization and interfacial control.