Annihilation mechanism of V-shaped pits in c-GaN grown by hydride vapor-phase epitaxy

An evident issue in performing GaN growth along the c-direction is the generation of V-shaped pits on its surface. Here, we investigated the transition of the angle of facets forming a V-shaped pit via three-photon excitation photoluminescence (3PPL). The intermittent doping of Ge was introduced to GaN growth to observe the growth front. The size of the V-shaped pit composed of { 10 1 ¯ 2 } facets decreased along the growth direction, whereas that composed of { 10 1 ¯ 1 } facets, increased. Furthermore, planar growths of c-GaN and semipolar GaN having various surface orientations revealed that the V-shaped pit composed of { 10 1 ¯ 2 } was likely to annihilate rather than that of { 10 1 ¯ 1 } under the growth condition of N2 carrier gas, which coincides with the result of 3PPL.