The negligible effects of miscut on indium aluminium nitride growth

InAlN has many potential applications in photonics and electronics, but the growth rate of high quality material with smooth surfaces remains low, at ∼4 nm/min, preventing its wider use in thicker structures such as distributed Bragg reflectors, although this is not a significant problem for thin structures like high electron mobility transistors. We have investigated the effects of the vicinal miscut angle on InAlN growth with the hope of increasing the growth rate at higher miscuts, whilst maintaining a smooth surface. InAlN/GaN/Sapphire structures were grown on substrates with three different miscuts (0°, 0.25° and 0.5°) according to two different recipes, with different growth rates. This change in substrate miscut angle had no effect on either the growth rate, the indium incorporation or the surface morphology assessed by atomic force microscopy. Both the surface roughness and the volume of indium present on the surface as indium droplets were unaffected. This negative result suggests that even when the terraces on the underlying pseudo-substrate are very closely spaced InAlN growth does not proceed by a step flow mode once epilayers are approximately 100 nm thick (although these results cannot be extrapolated to very thin layers). It also demonstrates that differing miscut angle is not an explanation for any differing properties of material produced by different groups.