Abstract: A semiconductor substrate includes a first silicon substrate, an oxide layer, a second silicon substrate, and an epitaxial layer. The oxide layer is disposed on the first silicon substrate. The second silicon substrate is disposed on the oxide layer. The second silicon substrate has a thickness between 10 nm and 10 ?m. The epitaxial layer is disposed on the second silicon substrate.

Abstract: A method of forming a GaN film includes following steps. A silicon-on-insulator (SOI) substrate is provided. The SOI substrate includes a substrate, an insulator layer and a silicon layer. The insulator layer is disposed on the substrate and the silicon layer is disposed on the insulator layer. The silicon layer is pattered into a patterned silicon layer including a plurality of recessed features. Each recessed feature has a sidewall. A plurality of GaN structures are epitaxially grown from the sidewalls, and the GaN structures are separated from each other. The GaN structures are continuously epitaxially grown vertically and horizontally to merge the GaN structures over top of the patterned silicon layer to form a GaN layer.

Abstract: A method of forming a GaN film includes following steps. A silicon-on-insulator (SOI) substrate is provided. The SOI substrate includes a substrate, an insulator layer and a silicon layer. The insulator layer is disposed on the substrate and the silicon layer is disposed on the insulator layer. The silicon layer is pattered into a patterned silicon layer including a plurality of recessed features. Each recessed feature has a sidewall. A plurality of GaN structures are epitaxially grown from the sidewalls, and the GaN structures are separated from each other. The GaN structures are continuously epitaxially grown vertically and horizontally to merge the GaN structures over top of the patterned silicon layer to form a GaN layer.