Reduction of threading dislocations in GaN overgrowth by MOCVD on TiN porous network templates

GaN overlayers for the purpose of reducing extended defects have been grown by MOCVD on porous network of TiN thin layers which in turn were achieved by in situ nitridation of thin Ti layers (20 nm and 10 nm) on a GaN template. TEM analyses performed for the GaN layer with 20 nm TiN porous netowrk indicate the effectiveness of TiN porous structure in blocking the threading dislocation from penetrating into the upper layer. Plan-view TEM indicated a reduction in the dislocation density by a factor of 10, compared to the GaN template without TiN network. Subsurface 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 is also confimed by X-ray diffraction data and time-resolved photoluminescence measurements at room temperature.