GaN decomposition in ammonia

GaN decomposition is studied as a function of pressure and temperature in m ixed NH3 and H-2 flows more characteristic of the MOVPE growth environment. As NH3, is substituted for the 6 SLM H-2 flow, the GaN decomposition rate at 1000 degreesC is reduced from 1x10(16) cm(-2) s(-1) (i.e. 9 monolayers/s ) in pure H-2 to a minimum of 1x10(14) cm(-2)s(-1) at an NH3 density of 1x1 0(19) cm(-3). Further increases of the NH3 density above 1x10(19) cm(-3) re sult in an increase in the GaN decomposition rate. The measured activation energy, E-A, for GaN decomposition in mixed H-2 and NH3 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 NH3 now conditions, the decomposition r ate increases and the growth rate decreases with the addition of trimethylg allium to the flow. The decomposition in mixed NH3 and H-2 and in pure H-2 flows behave similarly, suggesting that surface H plays a similar role in t he decomposition and growth of GaN in NH3.