Analysis of self-lift-off process during HVPE growth of GaN on MOCVD-GaN/sapphire substrates with photolitographically patterned Ti mask

An influence of a nitridation process on a self lift-off phenomenon during the HVPE crystallization of GaN on a MOCVD-GaN/sapphire template with photolitographically patterned Ti mask was investigated. Duration of the nitridation process and flows of reagents in this process were modified. A correlation between degradation degree of a GaN template surface and the conditions of the nitridation process was observed. It was also observed that the degree of degradation had a direct influence on a moment of the self lift-off phenomenon (separation of a HVPE-GaN crystal from the template). It was shown that the best free-standing HVPE-GaN crystals, in sense of their structural quality, were obtained when the separation process occurred during cooling down step.