Influence of Temperature-Dependent Substrate Decomposition on Graphene for Separable GaN Growth

Graphene has been adopted in III-V material growth since it can reduce the threading dislocations and the III-V epilayer can easily be separated from the substrate due to the weak chemical bond. However, depending on the substrate supporting the graphene, some substrates decompose in the III-V material growth environment, which results in the problem that no graphene remains. In this study, the influence of temperature-dependent substrate decomposition on graphene through an annealing process that resembles conventional growth conditions in metal-organic chemical vapor deposition (MOCVD) is investigated. It is also confirmed that trimethylgallium, hydrogen, and ammonia gases do not directly affect the graphene loss through gallium nitride (GaN) growth on a graphene/sapphire. In addition, GaN grown on graphene/sapphire could separate, but GaN grown on a graphene/GaN template could not be separated due to GaN template decomposition and related graphene damage. Through further investigation for graphene/gallium arsenide, it is deduced that the gallium generated by substrate decomposition does not play a major role in damage to the graphene but instead the nitrogen generated by substrate decomposition is closely related to it. These results suggest that it is very important to adopt a decomposition-free substrate that do not damage graphene during GaN growth in MOCVD.