Microstructures of InAs1−xSbx (x = 0.07–0.14) alloys and strained-layer superlattices
Growth of InAs1−xSbx alloys by metalorganic chemical vapor deposition at 475°C results in CuPt ordering even at Sb concentrations as low as x = 0.07-0.14. The two {111}B variants are present, but each exists separately in 1-2 μm regions. However, the ordering is incomplete: it occurs in platelet domains lying on habit planes tilted 30° from (001) within a disordered matrix and is not continuous at the atomic scale within the domains. This ordering apparently explains the reduction in infrared emission energies relative to the bandgaps of bulk alloys. Similar ordering is found in an InAs0.91Sb0.09/In0.g7Ga0.13As strained-layer superlattice with lower-than-expected emission energy. High-resolution images indicate that the superlattice layers flat and regularly spaced. Infrared LEDs have been made from such superlattices.