Metalorganic vapor phase epitaxy growth of crack-free AlN on GaN and its application to high-mobility AlN/GaN superlattices

We have succeeded in growing crack-free AlN of even 0.5 μm thickness on GaN by metalorganic vapor phase epitaxy. A (0001) sapphire substrate was used. Crack-free AlN was grown on GaN at 1000 °C with N2 carrier gas. An AlN layer was grown on GaN of 2 μm thickness grown at 1050 °C, following the low-temperature deposition of an AlN buffer layer of 30 nm. No cracks were observed in the microphotographs of AlN on GaN grown using N2. X-ray diffraction analysis revealed that AlN/GaN superlattices (SLs) were coherently grown on GaN, and satellite peaks up to the third order were observed. The structure of AlN/GaN SLs on GaN showed a maximum electron mobility of 1580 cm2/V s at room temperature and a nominal sheet carrier density of 8.4×1012 cm−2.