Heteroepitaxial Growth of GaN Film on Si substrate by Magnetron Sputtering

Abstract: In this study, the effect of AlN buffer layer structure and morphology on the GaN films deposited on Si (111) substrate by reactive DC magnetron sputtering have been studied. For structural and morphological characterization X-ray diffraction (XRD) and Scanning electron microscope (SEM) were used. It is found that AlN films without Al pre-deposition on Si have a poor crystalline quality due to the formation of an amorphous layer at Si/AlN interface. Various initial Al sputtering durations on Si substrate result in changing the AlN buffer layer’s quality and morphology and choosing proper deposition duration can improve AlN buffer layer and the subsequent GaN layer quality. It is found that more than 15 s Al pre deposition can suppress the amorphous layer formation and enhance the film quality. The Rocking curve FWHM for both in-plane and out-of-plane orientation decreased from 1.86 and 1.56   to 0.4   and 0.3  , respectively, by 4 minutes Al pre-deposition on Si, however, overlong Al deposition results in poor surface morphology. It is found that 15s Al deposition is sufficient to enhance the quality as well as keeping the surface relatively smooth. In addition, AlN films deposited at 1000   showed the best film quality. GaN films directly grown on Si showed a poor crystalline quality and surface morphology, improvement of quality and morphology was observed for GaN samples deposited on AlN buffer layer. Also, melt-back etching observed on the surface of GaN grown on Si without AlN buffer layer. It is found that duration of Al deposition has a significant effect on GaN surface morphology, Al layer deposition more than 15 s result in a rough surface for GaN films. With choosing the optimum duration of Al pre-deposition and proper growth temperature a good quality GaN with a smooth surface morphology can be produced.