Effects of growth temperature for in-situ deposited SiNx interlayer on structural and optical properties of semipolar (112¯2) AlGaN films

• High-quality semipolar ( 11 2 ¯ 2 ) AlGaN films were grown with an in-situ SiN x interlayer deposited from 700 to 1100 o C. • Significant improvements in surface morphology, crystalline quality, and optical properties. • The most effective improvement was obtained by the optimized SiN x interlayer deposited at 800 o C. • The degradation in surface morphology and crystalline quality when the SiN x interlayer deposited from 800 to 1100 o C. • A remarkable deterioration in crystalline quality and abrupt increase in the impurity-related yellow band emission at 700 o C or 1100 o C. The dependence of surface morphology, crystalline quality, and optical properties on the growth temperature of in-situ deposited SiN x interlayers in the semipolar ( 11 2 ¯ 2 ) AlGaN film was investigated intensively. The in-situ SiN x deposited interlayer was consisted of irregular ultra-thin SiN x nano-scale island-like structures as verified by using scanning electron microscope and energy dispersive spectroscopy. As the growth temperature of the in-situ deposited SiN x interlayer was increased from 700 to 1100 o C, the root mean square roughness of the semipolar ( 11 2 ¯ 2 ) AlGaN film increased from 0.72 to 0.87 nm. It was revealed that significant improvements in surface morphology, crystalline quality, and optical properties of the semipolar ( 11 2 ¯ 2 ) AlGaN films could be achieved with the insertion of an in-situ deposited SiN x interlayer grown at a temperature between 800 and 1000 o C. These achievements are owing to the formation of the SiN x nano-scale island-like structures that like the well-known patterned sapphire substrate played a crucial role in the reduction of the basal-plane stacking faults (BSFs) and the suppression of the BSFs- and other defects-related emissions in the semipolar ( 11 2 ¯ 2 ) AlGaN films.