Reduction in crystalline quality anisotropy and strain for non-polar a-plane GaN epi-layers with nano-scale island-like SiN interlayer

The reduction in the crystalline quality anisotropy and the in-plane strain for the non-polar a -plane GaN epi-layer with nano-scale island-like SiN x interlayer was studied extensively with scanning electron microscopy, high-resolution X-ray diffraction measurement, and Raman spectroscopy. It was demonstrated that the SiN x interlayer was powerful to suppress the crystalline quality anisotropy in the a -plane GaN epi-layer since the full width at half maximum values of the X-ray rocking curves for both c -direction and m -direction were reduced from 1108 to 780 arcsec and from 2077 to 806 arcsec, respectively. The Raman measurement results also reveal that the SiN x interlayer plays a crucial role in compensating the in-plane strains. In fact, the in-plane compressive strain along m -direction and the tensile strain along c -direction were found to be decreased by approximately 62% and 78%, respectively due to the insertion of the SiN x interlayer.