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 sit u 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 dec omposition 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 r ange above 850 degreesC. The decomposition rate as a function of the hydrog en partial pressure (P-H 2) has been observed. The rate-limiting reaction o f 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 tempera ture.