Navigating growth regimes in graphene-assisted III-nitride epitaxy: insights, challenges, and pathways forward

The technological impact of III-nitrides in lighting and power electronics is well established. However, heteroepitaxy on rigid foreign substrates often results in high defect densities and limited mechanical compliance. This poses hurdles for the exploitation of electronic and photonic integrated circuits. Graphene interlayers offer an appealing alternative: by weakening interfacial adhesion while maintaining crystalline alignment under specific epitaxy conditions, they facilitate the lift-off of freestanding nitride membranes, allowing for substrate reuse. This review maps the experimental landscape with the theoretical background of graphene-assisted III-nitride growth, connecting macroscopic outcomes to competing interfacial regimes of van der Waals (vdW) epitaxy, quasi-vdW epitaxy, thru-hole growth, and remote epitaxy. Each process has a specific operational window under metal-organic chemical vapor deposition (MOCVD) conditions. Central challenges associated with the selection of a regime are traced to the exact root causes: suppressed nucleation on pristine graphene, uncontrolled defect formation and contamination during graphene preparation, and graphene degradation or interfacial reactions under the aggressive MOCVD environment, each of which can shift the dominant regime. Recent advances in direct graphene synthesis, controlled functionalization, buffers, and flow-modulation schemes have been assessed as practical routes to coalesced, transferable GaN- and AlN-based membranes, which constitute the main focus of this review. Future priorities for field advancement include standardized metrics for distinguishing growth modes, robust interface engineering, and considerations for novel device creation.