Effect of aluminum carbide buffer layer on growth and self‐separation of m ‐plane GaN by hydride vapor phase epitaxy

An m ‐plane GaN layer with a thickness of approximately 500 μm was successfully obtained on a conventional m ‐plane sapphire substrate with a diameter of 2 inches. The GaN layer was grown by hydride vapor phase epitaxy (HVPE) on a buffer layer of low‐temperature (LT) GaN/Al 4 C 3 structure deposited on the sapphire substrate by metalorganic chemical vapor deposition (MOCVD). The deposition temperature of the Al 4 C 3 layer affected the appearance of the m ‐plane GaN layer. The c ‐axes of the GaN layer is parallel to the a ‐axis of the sapphire substrate. The thick GaN layer spontaneously separated from the sapphire substrate after its growth. Complete self‐separation of the m ‐plane GaN from the sapphire substrate was achieved with good reproducibility when the thickness of the Al 4 C 3 layer was 70–100 nm. By lapping and polishing the self‐separated GaN crystal, a freestanding m ‐plane GaN wafer with a diameter of 45 mm was obtained. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)