GaN Decomposition in Ammonia

Abstract

GaN decomposition is studied as a function of pressure and temperature in mixed NH3 and H2 flows more characteristic of the MOVPE growth environment. As NH3 is substituted for the 6 SLM H2 flow, the GaN decomposition rate at 1000 °C is reduced from 1×1016 cm-2s-1 (i.e. 9 monolayers/s) in pure H2 to a minimum of 1×1014 cm-2s-1 at an NH3 density of 1×1019 cm-3. Further increases of the NH3 density above 1×1019 cm-3 result in an increase in the GaN decomposition rate. The measured activation energy, EA, for GaN decomposition in mixed H2 and NH3 flows is less than the EA measured in vacuum and in N2 environments. As the growth pressure is increased under the same H2 and NH3 flow conditions, the decomposition rate increases and the growth rate decreases with the addition of trimethylgallium to the flow. The decomposition in mixed NH3 and H2 and in pure H2 flows behave similarly, suggesting that surface H plays a similar role in the decomposition and growth of GaN in NH3.