| abstract |
This GaN film manufacturing method includes: a step of preparing a composite substrate (10), which includes a supporting substrate (11) that dissolves in a hydrofluoric acid, and a single crystal film (13) disposed on the main surface (11m) side of the supporting substrate (11), and has a thermal expansion coefficient in the main surface (11m) of the supporting substrate (11) more than 0.8 times but less than 1.2 times a thermal expansion coefficient of a GaN crystal; a step of forming a GaN film (20) on the main surface (13m) of the single crystal film (13) disposed on the main surface (11m) side of the supporting substrate (11); and a step of removing the supporting substrate (11) by dissolving the supporting substrate in the hydrofluoric acid. Consequently, the GaN film manufacturing method whereby the GaN film having a large main surface area, small warpage, and excellent crystal characteristics is efficiently obtained, and the composite substrate used in the method are provided. |