The effects of varying metal precursor fluxes on the growth of InAlN by metal organic vapour phase epitaxy

InAlN is a relatively new addition to the palette of nitride semiconductor alloys, with potential applications in distributed Bragg reflectors and high electron mobility transistors. However relatively little is known about the effects of different growth conditions on InAlN’s structure and properties and more importantly what these effects can tell us about the surface processes of growth. Here we have investigated the effects of varying various metal fluxes. First, we varied the total fluxes of all the precursors while maintaining their ratios. This led to an increase in growth rate, of itself very desirable, but at the considerable cost of significantly roughened surfaces. Analysis of these surfaces using power spectral density functions suggests that they were all produced by a combination of stochastic roughening and smoothing by surface diffusion, suggesting that at a given temperature increasing the growth rate will always lead to roughening. In addition, we examined the effect of varying just the trimethylindium flux (and therefore varying the indium to gallium ratio). As this flux was increased the indium incorporation initially increased but then levelled off, and for further increases the amount of indium on the surface as droplets increases significantly, suggesting that there is a limit to the indium incorporation that than be achieved at a given temperature and pressure. This suggests that there are practical limits to simultaneously achieving high growth rates, high indium contents and low surface roughnesses.