Optimizing GaN (1122) hetero-epitaxial templates grown on (1010) sapphire

Abstract

The hetero-epitaxy of (1122) GaN on (1010) sapphire was optimized in metal-organic vapor phase epitaxy. Best results were obtained from an AlN nucleation followed by AlN and AlGaN layers, and inserting low-temperature AlN interlayers (ILs) as well as a SiNx IL. X-ray diffraction (XRD) of ω scans of the symmetric (1122) reflection yielded an ω FWHM <450″ along [1123] and <900″ along [1010] together with a 100×100μm2 rms roughness below 10nm as determined by atomic force microscopy. The lowest threading dislocation density achieved was ≈109cm-2 while the basal plane stacking fault density was in the lower 105cm-1 range as determined by transmission electron microscopy. The suppression of the unwanted (1013) phase was lower than 1 in 10,000 as judged from XRD.