Effects of Dual Moderate-Temperature-Grown AIN Interlayers on Structural and Optical Properties of Semipolar (1122) AIN Film

Abstract

High quality semipolar (1122) AlN films have been grown on (1010) m-plane sapphire substrates with the help of dual moderate-temperature-grown (MTG) AlN interlayers by using metal-organic chemical vapor deposition technology. The layer thickness of the semipolar (1122) AlN film was determined by employing relative optical transmittance spectrum measured with ultraviolet-visible spectrophotometer. The effect of the insertion of 80 nm-thick MTG AlN interlayer on structural and optical properties was investigated in detail based on the characterization results of the atomic force microscopy, high-resolution X-ray diffraction, and Raman spectroscopy. Comparing with the semipolar (1122) AlN film grown without the MTG AlN interlayer, both the surface morphology and crystalline quality of the semipolar (1122) AlN film grown with the insertion of dual 80 nm-thick MTG AlN interlayers have been improved significantly. In fact, the root mean square value of the surface roughness decreased from 3.5 to 1.4 nm, and the full width at half maximum value of X-ray rocking curve decreased from 1667 to 1174 arcsec, respectively. These facts reveal that the insertion of the dual MTG AlN interlayers is a powerful method to improve the surface morphology and crystalline quality of the semipolar (1122) AlN films owing to the formation of nanoscale patterned substrate-like structure and its blocking effect on the propagation of the dislocations.