LOW-TEMPERATURE MOCVD OF HG1-XCDXTE ON 311, 511, 711 AND SHAPED GAAS

The influence of six new GaAs substrate orientations on the surface morphology and defect hillocks of epitaxial Hg(1-x)Cd(x)Te (MCT) layers, grown by low temperature MOCVD, is investigated using Nomarski interference contrast microscopy and SEM. Smoother epitaxial layers are obtained on (311), (511) and (711) substrates of A or B polarity compared with growth on (100) or (100) 2-degrees off toward (110) substrates. The quality and orientation of the layers was monitored by X-ray techniques, Rutherford backscattering/channeling and selected area electron channeling patterns. Absolute polarity determination by X-ray diffraction confirmed that the epilayers adopted the polarity of the substrate. Conformal growth on contoured substrates revealed preferential facet formation and growth rate variation which leads to local composition changes in the interdiffused multilayer process. The growth hillocks commonly observed in epitaxy of MCT are related to the oval defects in III-V compounds, and dissolve on annealing.