Fully-relaxed n-AlGaN on AlN / Al2O3 templates using strain-relaxed super-lattice buffer layers

Abstract

Strain relaxation, surface morphology, and threading dislocations of 2.5–μm-thick n–Al0.6Ga0.4N, grown by metal–organic chemical vapor deposition on AlN/Al2O3 templates using strain relaxed super lattice (SRSL) buffer layers, are investigated. The SRSLs are consisted of 11–115 nm Al0.50Ga0.50N/23 nm Al0.75Ga0.25N multiple layers. The n–Al0.6Ga0.4N layer is fully strain relaxed and smooth surface morphology when grown on the SRSL with Al0.50Ga0.50N thickness over 69 nm. The full width at half maximum values of X–ray rocking curves of n-Al0.6Ga0.4N for (0002) and (101‾2) planes are 237 and 468 arcsec, respectively. The threading screw dislocations and threading edge dislocations are estimated as 1.2 × 108 cm−2 and 1.1 × 109 cm−2, respectively. The SRSL buffer layer enables to achieve 100% strain relaxation together with a smooth surface and a low threading dislocation density.