  In metal organic vapor phase epitaxy of GaN, the growth mode is sensitive to
reactor temperature. In this study, V-pit-shaped GaN has been grown on normal
c-plane cone-patterned sapphire substrate by decreasing the growth temperature
of high-temperature-GaN to around 950 oC, which leads to the 3-dimensional
growth of GaN. The so-called "WM" well describes the shape that the bottom of
GaN V-pit is just right over the top of sapphire cone, and the regular
arrangement of V-pits follows the patterns of sapphire substrate strictly. Two
types of semipolar facets (1101) and (1122) expose on sidewalls of V-pits.
Furthermore, by raising the growth temperature to 1000 oC, the growth mode of
GaN can be transferred to 2-demonsional growth. Accordingly, the size of V-pits
becomes smaller and the area of c-plane GaN becomes larger, while the total
thickness of GaN keeps almost unchanged during this process. As long as the
2-demonsional growth lasts, the V-pits will disappear and only flat c-plane GaN
remains. This means the area ratio of c-plane and semipolar plane GaN can be
controlled by the duration time of 2-demonsional growth.
