STRAIN-INDUCED COMPOSITIONAL SHIFT IN THE GROWTH OF INASYP1-Y ONTO (100) INP BY GAS-SOURCE MOLECULAR-BEAM EPITAXY

The growth of InAsxP1-x onto (100) InP by gas-source molecular beam ep itaxy was examined systematically, focusing on control of the resultin g As/P incorporation ratio. The group V fluxes were obtained by passin g phosphine and arsine through a dual-input low-pressure gas cracker. For a given flow ratio of the source gases, the arsenic fraction y of the resulting InAsxP1-x films is seen to increase with the film thickn ess over the first 1500 angstrom (1 angstrom = 10(-10) m) as indicated by secondary ion mass spectroscopy. Auger depth profiling and by Ruth erford backscattering spectroscopy. Thin, strained InAsyP1-y layers (0 .30 < y < 0.70, corresponding to a compressive strain of about 1.0-2.2 %) contain about 5-20% less As than similarly grown thicker. relaxed l ayers. For a given growth rate and substrate temperature. the relative compositional shift is found to be linearly proportional to the effec tive strain corresponding to y. Substrate temperatures above 475-degre es-C further reduce the incorporation ratio of As into both strained a nd relaxed InAsyP1-y layers. initially enhancing the strain-induced co mpositional shift. However, strain minimization via a compositional sh ift competes with a greater rate of relaxation of the InAsP lattice wi th film thickness at higher substrate temperatures.