Effect of temperature and carrier gas on the properties of thick I n x A l 1 - x N layer

Thick (>150 nm) ${In}_x{Al}_{1-x}$N layers were grown on GaN/sapphire (0 0 0 1) by organometallic vapor phase epitaxy. Growth temperature of ${In}_x{Al}_{1-x}$N layers was reduced from 790 to 730 °C, to examine the effects of growth temperature in ${In}_x{Al}_{1-x}$N layers grown under $H_2$ carrier gas. Indium incorporation, surface morphology, electrical, and optical properties of ${In}_x{Al}_{1-x}$N layers were examined as a function of growth temperature. Increase in In-molar fraction, as determined by high resolution X-ray diffraction, was observed with decreasing growth temperature of ${In}_x{Al}_{1-x}$N layers at the expense of surface roughness. Unstrained ${In}_x{Al}_{1-x}$N layer was achieved at 730 °C under $H_2$ carrier gas with x = 0.18. However, ${In}_x{Al}_{1-x}$N layer grown under $N_2$ carrier gas at 730 °C to study the effects of carrier gas, was observed with two times higher In-molar fraction (x = 0.37) and one order lower carrier concentration. This work shows the essential requirement of a multi-characterization approach to establish a connection between structural, electrical, and optical properties to improve our understanding towards ${In}_x{Al}_{1-x}$N. Edge threading dislocations density is found to be the most important parameter in deciding the characteristics of an ${In}_x{Al}_{1-x}$N layer.