Microstructural and Optical Properties of AlxGa1-xN/GaN Heterostructure Thin Films Grown on Si(111) Substrate by Plasma Assisted Metalorganic Chemical Vapor Deposition Method

Abstract

The microstructure and optical properties of AlxGa1-xN/GaN heterostructures thin films grown on Si(111) substrate by Plasma Assisted-Metalorganic Chemical Vapor Deposition (PA-MOCVD) with various of TMAl flow rate from 0.05 to 0.13 sccm have been investigated. The x values of AlxGa1-xN thin films were determined by NIR-UV visible optical reflectance spectroscope. The crystalline plane orientation and surface morphology of films were determined by X-ray diffractometer (XRD) and scanning electron microscope (SEM), respectively. The films with x = 0.29 and x = 0.36 have single crystalline orientation of (1010) plane while the film with x = 0.12 has two crystalline orientation of (1010) and (1011) planes. The surface morphology of films depend on the x value of film, which is the film with higher of x value showed the smaller grain size and the smoother surface. The patterns of optical reflectance show that the ordered of oscillation depend on smoothness of film surface, on the other hand the number of oscillation related to the thickness of films. These results were confirmed by surface morphology and cross section of films with means of SEM images. Band to band absorption mechanism (≈band gap energy, Eg) were indicated by the end of the peak oscillation position obtained that the Eg of GaN thin films was 3.34 eV and the Eg of AlxGa1-xN thin films were ranged from 3.34 to 6.20 eV, depend on the x values of films.