GaN Decomposition in Ammonia

GaN decomposition is studied as a function of pressure and temperature in mixed NH 3 and H 2 flows more characteristic of the MOVPE growth environment. As NH 3 is substituted for the 6 SLM H 2 flow, the GaN decomposition rate at 1000 °C is reduced from 1×10 16 cm −2 s −1 (i.e. 9 monolayers/s) in pure H 2 to a minimum of 1×10 14 cm −2 s −1 at an NH 3 density of 1×10 19 cm −3 . Further increases of the NH 3 density above 1×10 19 cm −3 result in an increase in the GaN decomposition rate. The measured activation energy, E A , for GaN decomposition in mixed H 2 and NH 3 flows is less than the E A measured in vacuum and in N 2 environments. As the growth pressure is increased under the same H 2 and NH 3 flow conditions, the decomposition rate increases and the growth rate decreases with the addition of trimethylgallium to the flow. The decomposition in mixed NH 3 and H 2 and in pure H 2 flows behave similarly, suggesting that surface H plays a similar role in the decomposition and growth of GaN in NH 3 .