High quality AlGaN growth by changing growth pressure and insertion of AlN/GaN superlattice interlayer

摘要

We have investigated the optical and structural properties of thick AlGaN layer grown using strain-relief AlN/GaN superlattice buffer on SiC/Si(111) substrate by low pressure metal organic chemical vapor deposition. A set of five period AlN/GaN superlattice interlayers was one of the most efficient methods for the strain relief by reducing biaxial tensile strain between GaN and AlGaN layer. A set of five period AlN/GaN superlattice interlayer and a thick AlGaN layer were grown by changing the growth pressure from 80 mbar to 100 mbar. The quality of AlGaN layer strongly depends on the pressure of growth of the AlN/GaN superlattice interlayer and AlGaN layer. The optimized pressure for the AlN/GaN superlattice interlayer and thick AlGaN layer was 80 mbar and 100 mbar, respectively. Crystal quality and morphology of AlGaN films improved and crack density reduced by using two-step growth method, remarkably.