The high density of threading dislocations, often leading to the formation of inverted hexagonal pits in InGaN/GaN heterostructures on sapphire substrates, lowered the radiative efficiency of light-emitting devices. Here, a cracked AlGaN template was implemented as a strain-relaxed layer for the subsequent growth of InGaN/GaN heterostructures. The detailed electron microscopy and surface topographic analyses showed that such a template had led to a reduction in threading dislocation density; especially for screw dislocations and V-pits in the overgrown InGaN/GaN layers. The relaxed re-growth of such heterostructures also led to an improved crystalline quality and higher In incorporation in InGaN. The improvement in the optical and structural quality of these InGaN/GaN layers was investigated by means of photoluminescence spectroscopy and transmission electron microscopy.

Reduction of V-Pit and Threading Dislocation Density in InGaN/GaN Heterostructures Grown on Cracked AlGaN Templates. C.B.Soh, S.Y.Chow, S.Tripathy, S.J.Chua: Journal of Physics - Condensed Matter, 2008, 20[9], 095210 (6pp)