An in situ technique for reducing the threading dislocation density of an AlxGa1-xN buffer within sub micron-thick growths was demonstrated by using metal-organic vapor-phase epitaxy. A marked reduction in the threading dislocation density of an AlGaN buffer on a SiC substrate was achieved by inserting superlattices which consisted of highly Si-doped AlGaN and undoped AlGaN layers. The threading dislocation density of AlGaN decreased from 2 x 1010 to 7 x 107/cm2 upon inserting superlattices with a total growth thickness of 0.8µm. The Si incorporation into the highly Si-doped AlGaN layers of the superlattices was estimated to be about 1.2 x 1020/cm3 (0.24%). This strictly in situ technique did not require complicated processing, and the surface remained flat throughout. The method was suggested to be especially useful on SiC wafers; to prevent cracking in thin growth layers.

Fabrication of a Low-Threading-Dislocation-Density AlxGa1–xN Buffer on SiC using Highly Si-Doped AlxGa1–xN Superlattices. H.Hirayama, M.Ainoya, A.Kinoshita, A.Hirata, Y.Aoyagi: Applied Physics Letters, 2002, 80[12], 2057-9