Growth by MOCVD of In(Ga)AlN alloys, and a study of gallium contamination in these layers under nitrogen and hydrogen carrier gas

Abstract

We have studied the growth of In(Ga)AlN under nitrogen and hydrogen, changing the precursor flows, temperature and growth rate to examine the effect of these parameters on the indium incorporation and layer morphology. Under hydrogen carrier gas, we successfully incorporated indium into the layers by reducing the temperature below 620°C. We have also studied the gallium contamination in In(Ga)AlN layers, finding a linear correlation between tri-methyl indium (TMIn) flow and tri-methyl gallium (TMGa) effective flow coming from the pollution source, thought to be due to desorption from the chamber. By performing a chamber cleaning process between the GaN pseudo-substrate and the InAlN layer, we have both eliminated the gallium contamination and increased the indium content in our layers, reaching indium levels of up to 11% under hydrogen. Finally, we achieved a sheet resistance of 250Ω/sq on wafers with a clean between the GaN and the InAlN layers, showing the potential for using this technique to produce high performance devices.