Wurtzite GaN films have been grown on (001) Si substrates using&ggr;-Al2O3as an intermediate layer by low pressure(∼76 Torr)metalorganic chemical vapor deposition. Reflection high energy electron diffraction and double crystal x-ray diffraction measurements revealed that the thin&ggr;-Al2O3layer of “compliant” character was an effective intermediate layer for the GaN film grown epitaxially on Si. The narrowest linewidth of the x-ray rocking curve for (0002) diffraction of the 1.3 &mgr;m GaN sample was 54 arcmin. The orientation relationship ofGaN/&ggr;-Al2O3/Siwas (0001) GaN‖(001)&ggr;-Al2O3‖(001)Si, [11–20] GaN‖[110]&ggr;-Al2O3‖[110]Si. The photoluminescence measurement for GaN at room temperature exhibited a near band-edge peak of 365 nm (3.4 eV). ©1998 American Institute of Physics.