In situ measurements of GaN nucleation layer decompostion

Koleske, D. D.; Coltrin, M. E.; Allerman, A. A.; Cross, K. C.; Mitchell, C. C.; Figiel, J. J.
February 2003
Applied Physics Letters;2/24/2003, Vol. 82 Issue 8, p1170
Academic Journal
GaN nucleation layer (NL) decomposition was measured using optical reflectance over a wide range of pressure P, temperature T, and H[SUB2]/NH[SUB3] gas mixture. The GaN NLs show measurable decomposition above 800°C and do not significantly roughen until above 960°C. The NL decomposition rates increase with increasing P, increasing T, and decreasing NH[SUB3] flow. An activation energy E[SUBA] of 2.68 eV was measured (from 820 to 960°C) for NL decomposition and an E[SUBA] of 2.62 eV was measured (from 900 to 1075°C) for decomposition of thick, high-T bulk GaN films. Depending on P, the pre-exponential factor A[SUB0] was four to nine times larger for NL decomposition compared to bulk GaN decomposition. The E[SUBA] (measured for both NL and bulk GaN decomposition in mixed H[SUB2] and NH[SUB3] flows is similar to the E[SUBA] for Ga desorption, suggesting that the rate-limiting step for both NL and bulk GaN decomposition is Ga desorption.


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