Growth Characterization of Low-Temperature MOCVD GaN–Comparison between N2H4 and NH3–

The reaction mechanisms of the low-temperature growth of GaN using TMG (trimethylgallium) and two different nitrogen sources, i.e., N2H4 and NH3, are presented. Quite the same temperature dependence of the growth rate for both N sources was found, suggesting that the transport and decomposition of TMG are growth-rate limiting. A different behavior between the two N sources, on the other hand, is that the flow rate of NH3 that was required to obtain a specular surface of the film was much larger than that of N2H4. This surface specularity could be well described in terms of V/III (input gas molar ratio between N source and TMG) for the case of N2H4, whereas for the NH3 case, V/H2(NH3 partial pressure) was important. A discussion of the detailed growth mechanism, especially the difference in the two N sources, is presented.