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

Remote epitaxy via graphene has acquired much attention because of its potential for epi-layer mechanical exfoliation. The stability of graphene during the epitaxy process is a key point in realizing epi-layer exfoliation. In this work, GaN and AlN buffer layers were grown on a graphene-coated AlN/sapphire template and studied for the stability of graphene during the different stages of III-nitrides’ remote epitaxy. The annealing experiments of graphene in different atmospheres illustrate that N 2 carrier gas is the better choice to protect graphene. The graphene transition layer can remain stable during the low-temperature GaN or AlN buffer growth process, making the epi-layer exfoliable. However, when the temperature increased to a common value for GaN growth in MOCVD, recrystallization of the buffer layers happened and the graphene transition layer could be destroyed. As a result, the epi-layers cannot be exfoliated in this case. These results illustrate that the recrystallization process should be avoided or weakened to achieve exfoliation of the epi-layer.