Etch-decoration reveals that the rate of removal of carbon atoms exposed at monolayer steps on graphite surfaces is very different from the rate of removal, under identical conditions, at multilayer steps. At 1113 degrees K and a pressure of 1.33 newtons per square meter of oxygen, the rate of oxidation (along the layer planes) is less by a factor of nearly 100 than that at multilayer steps.

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We report for the first time, the metalorganic vapor phase epitaxy (MOVPE) growth of the quaternary alloy GaxAlyIn1−x−yAs, lattice matched to InP. Single epitaxial layers were prepared showing specular morphologies and lattice matching within Δa/a=10−3. Epilayers showed a high degree of crystallinity with routine x-ray linewidths of 20–40 seconds of arc. The lowest linewidth achieved was 22 seconds of arc. Room temperature and 4 K photoluminescence (PL) studies demonstrated very narrow excitonic transitions with ΔE at 4 K down to 5.4 meV. Band-gap energies, obtained from the absorption edge and PL peak energies, plotted against Al composition showed that the alloy was best described by a straight line relationship between the ternary end points, Ga0.47In0.53As and Al0.48In0.52As with no bowing observed.

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High quality Alo.481no.52As layers with specular morphology and narrowest reported x-ray linewidths of 24 seconds of arc have been grown on InP substrates by LP MOVPE at temperatures of 680-710 "C. Background carrier concentrations were in the range 8 X 15l5-4x 10"j cm 3 with room temperature mobilities as high as 1900 cm2 V" S " for growth under optimum conditions. Doping in the range IO"-2x 10l8 cm-3 was achieved using a H2S/H2 mixture. Improvements in structural and electrical quality were concurrent with successful Schottky barrier measurements where barrier heights of u p to q%, =O. 73 eV were obtained from C-V measurements on diodes using evaporated PtAu. These results have important implications in t h e development of Gao.,,In,,,As/AIo,481no.52~s HEMTS and InP-based opto-electronic devices.