Characterization of surface roughness of Pt Schottky contacts on quaternary n-Al0.08In0.08Ga0.84N thin film assessed by atomic force microscopy and fractal analysis

Abstract

The purpose of this study was to analyze surface topography of Pt Schottky contacts on quaternary n-Al0.08In0.08Ga0.84N thin film. To understand how the effect of temperature changes the layers surface, the surface topography was characterized through atomic force microscopy (AFM) and fractal analysis. Pt Schottky contacts grown on nanostructure Al0.08In0.08Ga0.84N thin film grown by molecular beam epitaxy technique on sapphire substrate at annealing temperatures range of 300–500 °C were used. AFM analysis was performed in contact mode, on square areas of 10 × 10 μm2, by using a Nanosurf Easyscan 2 AFM system. Detailed surface characterization of the surface topography was obtained using statistical parameters of 3D surface roughness, according with ISO 25178-2: 2012, provided by the AFM software. The results revealed that the high quality Schottky contact with the Schottky barrier heights and ideality factor of 0.76 and 1.03 respectively can be obtained under 30 min annealing at 400 °C in N2 ambience. The surface roughness of Pt Schottky contacts on quaternary n-Al0.08In0.08Ga0.84N thin film revealed a fractal structure at nanometer scale. Results obtained by fractal analysis confirm the relationship between the value of the fractal dimension and the statistical surface roughness parameters. AFM and fractal analysis are accurate tools that may assist manufacturers in developing Pt Schottky contacts on quaternary n-Al0.08In0.08Ga0.84N thin film with optimal surface characteristics and provides different yet complementary information to that offered by traditional surface statistical parameters.