In our study, we found that threading dislocation density (TDD) in GaN crystals naturally reduced from similar to 10(9) cm(-2) in a seed to less than similar to 10(3) cm(-2), just by using the small sized seed called a "point seed". However, the mechanism of the dramatic reduction was unclear In order to reveal the mechanism of this substantial reduction of TDD, we investigated the relationship between TDD and the crystal habit during the growth. Cathodoluminescence (CL) and scanning electron microscopy (SEM) images showed that TDD was dramatically reduced after the c face became small ( < 50 x 50 mu m(2)) in the habit-change process caused by changes of supersaturation during growth, in which bunched steps growing from the edge of the c face coalesced at the center. It is thought that the shrinking of the c face in the growth process enabled the coalescence of bunched steps, which led to the gathering of threading dislocations (TDs), and resulted in the dramatic reduction of TDD. We concluded that the natural reduction of TDs was caused by coalescence of bunched steps, which easily occurs in during the Na-flux growth on small-sized "point seeds", and which allowed fabrication of low-dislocation-density GaN wafers. (C) 2015 Elsevier B.V. All rights reserved.