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Heteroepitaxial Growth on Sapphire Substrates

Gallium nitride phosphide (GaN1-xPx) was epitaxially deposited on sapphire substrates by the vapor phase reaction of the Ga–Br2–NH3–PH3–N2 system. It was found that the composition x and the growth rate of the GaN1-xPx single crystal strongly depend on the substrate temperature and the flow rate of PH3 introduced into a reaction tube. The composition x increased with decreasing substrate temperature. The maximum composition x obtained was 0.064 at a substrate temperature of 1000degC. The growth rate increased with increasing flow rate of PH3 introduced into the reaction tube. At a substrate temperature of 1030degC, the growth rate of GaN1-xPx(x≈0.05) was 22 times larger than that of GaN. The diffraction lines observed on back-reflection divergent beam patterns of the GaN1-xPx single crystal were broad and did not show the separation due to Kα1 and Kα2 radiation.

Consistently low dislocation density midwavelength infrared (x=0.31) liquid phase epitaxy HgCdTe epitaxial layers with excellent morphology were grown on 2 in. sapphire substrates (PACE‐1) using a new low‐temperature (420 °C) Te melt process. Surface etch pit densities (EPDs) between 5×105 and 9×105 cm-2 were revealed using a previously reported chemical etch [J. S. Chen, US Patent No. 4897152] on a 20‐layer sample set. Cross‐sectional EPD profiles reveal a more rapid decrease of defects from the CdTe buffer layer interface as compared to conventionally grown (500 °C) material. X‐ray rocking curve widths from 43 to 66 arcsec were routinely observed. 77 K electron mobilities as high as 51 000 cm2/V‐s were measured. Secondary‐ion mass spectrometry profiles show a minimum of impurity gettering at the HgCdTe/CdTe buffer layer interface.


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