It is demonstrated that the density of threading dislocation in GaN is drastically reduced by utilizing regrowth technique on grooved stripe structure. The threading dislocations in GaN regrown on grooves tend to propagate off the c-axis so that an area with significantly reduced dislocation density is formed above the grooves. As a result, the threading dislocation density was reduced from 5 x 10(9) to 6.3 x 10(6) cm(-2).