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 mu m 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. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim