A free-standing GaN substrate, over 5cm in size, was prepared for the first time via hydride vapour-phase epitaxy; using GaAs as the starting substrate. A GaAs (111)A substrate, with a SiO2 mask pattern on its surface, was used. A thick GaN layer was grown onto the GaAs substrate, at 1030C, through openings in the mask. By dissolving the GaAs substrate, a free-standing GaN substrate which was about 500μm thick was obtained. The dislocation density in the GaN substrate was estimated, using plan-view transmission electron microscopy, to be as low as 2 x 105/cm2.

Preparation of Large Free-Standing GaN Substrates by Hydride Vapour Phase Epitaxy Using GaAs as a Starting Substrate. K.Motoki, T.Okahisa, N.Matsumoto, M.Matsushima, H.Kimura, H.Kasai, K.Takemoto, K.Uematsu, T.Hirano, M.Nakayama, S.Nakahata, M.Ueno, D.Hara, Y.Kumagai, A.Koukitu, H.Seki: Japanese Journal of Applied Physics - 2, 2001, 40[2B], L140-3