Synthesis and characterization of silicon-doped polycrystalline GaN films by r.f. sputtering

Silicon-doped polycrystalline GaN films were successfully deposited at temperatures ranging from 300 to 623 K on fused silica and silicon substrates by radio frequency (r.f.) magnetron sputtering at a system pressure of ∼5 Pa. The films were characterized by optical as well as microstructural measurements. The optical properties were studied by UV–vis–NIR spectrometer and photoluminicence (PL) measurements. The microstructural information was obtained from scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM) and X-ray diffraction (XRD) studies. PL measurement at 80 K exhibited two strong transitions located at ∼2.1 and ∼2.7 eV along with lower intensity peaks for luminescence at the higher energy side at ∼3.45 and ∼3.3 eV for all the films deposited here, and the peaks at ∼3.45 and ∼3.3 eV could be ascribed to transitions related to excitons bound to a neutral donor for h-GaN and c-GaN, respectively. A broad peak at ∼2.1 eV indicated the presence of yellow luminescence in all the films. The SEM and AFM images revealed that the films are compact with well-dispersed polycrystalline constituting the films. The XRD traces contained the signature of both the hexagonal and cubic phases of GaN.