Comprehensive strain and band gap analysis of PA-MBE grown AlGaN/GaN heterostructures on sapphire with ultra thin buffer

In this work, cluster tool (CT) Plasma Assisted Molecular Beam Epitaxy (PA-MBE) grown AlGaN/GaN heterostructure on c-plane (0 0 0 1) sapphire (Al2O3) were investigated by High Resolution X-ray Diffraction (HRXRD), Room Temperature Raman Spectroscopy (RTRS), and Room Temperature Photoluminescence (RTPL). The effects of strain and doping on GaN and AlGaN layers were investigated thoroughly. The out-of-plane ('c') and in-plane ('a') lattice parameters were measured from RTRS analysis and as well as reciprocal space mapping (RSM) from HRXRD scan of (002) and (105) plane. The in-plane (out-of plane) strain of the samples were found to be -2.5 x 10(-3) (1 x 10(-3)), and -1.7 x 10(-3) (2 x 10(-3)) in GaN layer and 5.1 x 10(-3) (-3.3 x 10(-3)), and 8.8 x 10(-3) (-1.3 x 10(-3)) in AlGaN layer, respectively. In addition, the band structures of AlGaN/GaN interface were estimated by both theoretical (based on elastic theory) and experimental observations of the RTPL spectrum. (C) 2014 Author(s).