In situ gravimetric monitoring of decomposition rate from GaN (0001) and (000(1)over-bar) surfaces using freestanding GaN

Polarity dependence on GaN decomposition has been investigated by an in situ gravimetric monitoring (GM) method using freestanding GaN (0001). In the H-2 carrier gas ambient, the decomposition rate of both GaN (0001) and GaN (000 (1) over bar) increased with increasing Substrate temperature. The decomposition rate of GaN (0001) was faster than that of GaN (000 (1) over bar) at temperatures below 820 degreesC. whereas the decomposition rate of GaN (000 (1) over bar) was faster than that of GaN (0001) in the temperature range above 850 degreesC. The decomposition rate as a function of the hydrogen partial pressure (P-H 2) has been observed. The rate-limiting reaction of the GaN decomposition on both surfaces is shifted from N(surface)+3/2H(2)(g)--> NH3(g) to Ga(surface)+ 1/2H(2)(g)--> GaH(g) with increase of temperature.