NH3-free growth of GaN nanostructure on n-Si (1 1 1) substrate using a conventional thermal evaporation technique

Abstract

We have investigated the influence of carrier gas on grown gallium nitride (GaN) epitaxial layers deposited on n-Si (111) by a physical vapour deposition (PVD) via thermal evaporation of GaN powder at 1150°C. The GaN nanostructures were grown at a temperature of 1050°C for 60min under various gases (N2, H2 mixed with N2, and Ar2) with absence of NH3. The morphology, structure, and optical properties (SEM) images showed that the morphology of GaN displayed various shapes of nanostructured depending on the type of carrier gas. X-ray diffraction (XRD) pattern showed that the GaN polycrystalline reveals a wurtzite-hexagonal structure with [001] crystal orientation. Raman spectra exhibited a red shift in peaks of E2 (high) as a result of tensile stress. Photoluminescence (PL) measurements showed two band emissions aside from the UV emission. The ultraviolet band gap of GaN nanostructure displayed a red shift as compared with the bulk GaN; this might be attributed to an increase in the defect and stress present in the GaN nanostructure. In addition, the observed blue and green–yellow emissions indicated defects due to the N vacancy and C impurity of the supplied gas. These results clearly indicated that the carrier gas, similar to the growth temperature, is one of the important parameters to control the quality of thermal evaporation (TE)-GaN epilayers.