AlN/GaN Short-Period Superlattice Coherently Grown on 6H-SiC(0001) Substrates by Molecular Beam Epitaxy

We demonstrate the coherent growth of AlN/GaN short-period superlattice (SPSL) on 6H-SiC(0001) substrates by molecular beam epitaxy. A high-quality 5-nm-thick AlN layer was grown on SiC as a template layer, followed by the growth of AlN (12 BL)/GaN (2 BL) SPSL, which consists of 40 periods (total thickness: 140 nm). The SPSL was coherently grown on SiC, and its threading dislocation density (TDD) was as low as 8×108 cm-2. The SPSL, which had 3-BL-thick GaN layers, was relaxed, and the TDD increased to 8×1010 cm-2.