GaN overlayers for the purpose of reducing extended defects were grown by MOCVD on porous network of TiN thin layers which in turn were achieved by in situ nitridation of thin Ti layers (20 and 10nm) on a GaN template. Transmission electron microscopic analyses performed for the GaN layer with 20nm TiN porous network indicated the effectiveness of TiN porous structure in blocking the threading dislocation from penetrating into the upper layer. Plan-view transmission electron microscopy indicated a reduction in the dislocation density by a factor of 10, compared to the GaN template without TiN network. Sub-surface voids were formed during the TiN formation, which act as defect concentrators, and termination sites for dislocations. The reduction in defect density through the use of TiN porous networks was also confirmed by X-ray diffraction data and time-resolved photoluminescence measurements at room temperature.

Reduction of Threading Dislocations in GaN Overgrowth by MOCVD on TiN Porous Network Templates. F.Yun, Y.Fu, Y.T.Moon, Ü.Özgür, J.Q.Xie, S.Doğan, H.Morkoç, C.K.Inoki, T.S.Kuan, L.Zhou, D.J.Smith: Physica Status Solidi A, 2005, 202[5], 749-53