The in situ deposition of SiNx masks by metal-organic vapour phase epitaxy was

optimized to achieve c-plane oriented GaN layers on sapphire having a dislocation

density of less than 2 x 108/cm2. The defect termination was found to be most

efficient if the SiNx was located after the growth of 100nm GaN, whereas when

deposited directly onto the AlN nucleation it was less efficient but yielded highly

compressively strained layers indicated by a donor-bound exciton peak position of

3.493eV in photoluminescence (13K). Furthermore it was observed via in situ reflectometry that a higher deposition temperature during the silane treatment

strongly increased the surface roughening to yield faster coalescence during the

GaN overgrowth but finally influenced 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.

Process Optimization for the Effective Reduction of Threading Dislocations in

MOVPE Grown GaN Using in situ Deposited SiNx Masks. J.Hertkorn, F.Lipski,

P.Brückner, T.Wunderer, S.B.Thapa, F.Scholz, A.Chuvilin, U.Kaiser, M.Beer,

J.Zweck: Journal of Crystal Growth, 2008, 310[23], 4867-70