Microstructure and optical properties of AlxGal_xN/GaN heterostructures thin films grown on Si(111)substrate by Plasma Assisted-Metalorganic Chemical Vapor Deposition (PA-MOCVD) were investigated. The surfacemorphology and crystal orientation of the films were determined by scanning electron microscope (SEM) and X-raydiffractometer (XRD), respectively. The content of Al in AlxGal_xNfilms (x) was determined by means of NIR-UVvisible optical reflectance spectroscope. The surface morphology of films depends significantly on the content of AI.Films with higher value of x showed the smaller grain size and the smoother surface. Films with x = 0.29 and x = 0.36showed crystal orientation of (1010) plane, while films with x = 0.12 have two crystal orientation of (1010) and (1011)planes. The optical reflectance spectra showed that the ordered of oscillation depend on the smoothness of the filmsurface, while the number of oscillation related to the thickness of films. The calculated band gap was 3.34 eV for GaNand in the range of 3.34 to 6.20 eV for AlxGal_xNdepending on the x values.Keywords: AlxGal_xN/GaN,MOCVD, crystal structure, optical reflectance.PACS: 78.55.Cr, 78.66.Fd. H. Sutantol,2, A. Subagiol,2, E. Supriyanto1,3, P. Arifinl,M. Budimanl, Sukimol, M. BarmawilJ Laboratory of Electronic Material Physics, Bandung Institute ofTecll1lology, BandungJI. Ganesha No. 10 Bandung 40132, Indonesia2Department of Physics, Diponegoro University, SemarangKampus MIPA-UNDIP, Jl. Prof. Soedharto, SR, Tembalang-Semarang 50275, Indonesia3Department of Physics, Jember University, JemberJI. Kalimantan 1Il/25Kampus Tegalboto-Jember, Indonesia
