Process optimization for the effective reduction of threading dislocations in MOVPE grown GaN using in situ deposited [formula omitted] masks

Abstract

In this study the in situ deposition of SiN x masks by metalorganic vapor phase epitaxy (MOVPE) has been optimized to achieve c -plane oriented GaN layers on sapphire with a dislocation density < 2 × 10 8 cm - 2 . The defect termination was found to be most efficient if the SiN x is located after the growth of 100 nm GaN, whereas deposited directly on the AlN nucleation it was less efficient but yielded highly compressively strained layers indicated by a donor bound exciton peak position of 3.493 eV in photoluminescence (13 K). Furthermore we observed by in situ reflectometry that a higher deposition temperature during the silane treatment was strongly increasing the surface roughening yielding a faster coalescence during the GaN overgrowth but finally influencing the defect termination negatively. In terms of lateral overgrowth a high V/III ratio (2D growth mode) was most efficient in terms of defect reduction, whereas a 3D–2D-process at lower V/III ratio yielded much faster overgrowth but influenced the defect termination negatively.