Experimental and theoretical study of the growth of GaN on sapphire by HVPE

We study the influence of the reactor geometry and the control of the parasitic deposits on the growth of GaN by HVPE. Growth rates around 100 mu m/h have been obtained with gas outlets close to the substrate and 16 mu m/h with homogeneous vapour. The quality of the epitaxial layer deteriorates while the growth rate increases with decreasing distance between gas outlets and substrate, and the increase of the parasitic deposit. We predict by a model that in a homogeneous vapour and for a deposited mass on the quartz wall up to 0.86 g/h, the growth rate decreases drastically at high temperature down to etching. Adding HCl to the main nitrogen now, the parasitic deposit decreases and the growth rate stays constant.