Self-Exfoliation in Quasi-van der Waals Epitaxy of III-Nitrides on Hexagonal Boron Nitride

Van der Waals (vdW) epitaxy offers a promising route for growing III-nitride semiconductors without traditional substrate constraints. Among its unique capabilities, spontaneous self-exfoliation─where grown layers automatically separate from substrates─could revolutionize device fabrication by eliminating complex removal processes. However, the underlying mechanisms controlling this phenomenon remain unclear, hindering reliable implementation. This study investigates the self-exfoliation in gallium nitride (GaN) films grown via metal–organic chemical vapor deposition (MOCVD) on hexagonal boron nitride (h-BN) templates and discovered that h-BN structural integrity determines exfoliation behavior. An optimized aluminum gallium nitride (AlGaN) buffer strategy was developed (910 °C, 15 min), which has been shown to protect the integrity of h-BN during subsequent growth. Comparing GaN film growth on as-grown versus transferred h-BN substrates revealed a critical distinction: self-exfoliation occurs exclusively on as-grown h-BN, while transferred h-BN is destroyed during growth, preventing separation. The driving mechanism involves thermal expansion differences that generate compressive stress exceeding h-BN’s weak interlayer bonding during cooling. Self-exfoliated films demonstrate exceptional strain relaxation (residual stress <0.05 GPa) and successful transfer to arbitrary substrates, enabling applications in flexible electronics, micro-LED displays, and heterogeneous integration.