Influence of Graphene Stability on III-Nitride Remote Epitaxy for Exfoliation

Remoteepitaxy via graphene has acquired much attention becauseof its potential for epi-layer mechanical exfoliation. The stabilityof graphene during the epitaxy process is a key point in realizingepi-layer exfoliation. In this work, GaN and AlN buffer layers weregrown on a graphene-coated AlN/sapphire template and studied for thestability of graphene during the different stages of III-nitrides'remote epitaxy. The annealing experiments of graphene in differentatmospheres illustrate that N-2 carrier gas is the betterchoice to protect graphene. The graphene transition layer can remainstable during the low-temperature GaN or AlN buffer growth process,making the epi-layer exfoliable. However, when the temperature increasedto a common value for GaN growth in MOCVD, recrystallization of thebuffer layers happened and the graphene transition layer could bedestroyed. As a result, the epi-layers cannot be exfoliated in thiscase. These results illustrate that the recrystallization processshould be avoided or weakened to achieve exfoliation of the epi-layer.