Nucleation mechanism of GaN growth on wet etched pattern sapphire substrates

Patterned sapphire substrates (PSS) are generally applied and have been proved to be effective in the increasing light extraction efficiency and crystal quality of GaN-based LEDs. The time evolution growth of GaN on triangle platform shaped PSS with an n-plane inclined surface and triangle cone shaped PSS with a part r-plane surface has been performed to research the nucleation and 3D growth mechanisms of GaN grown on the PSS. After the low temperature GaN growth process and high temperature ramping process, the small islands of GaN rotate and gather on the n-plane surface near the ridges of the triangle platform shaped PSS. Then the next 850 seconds high temperature growth process of GaN shows a 3D behavior. From the observations of SEM, it is believed that <1−100>, <11−20> and <0001> are the three preferred growth directions for GaN and the (1−10k) and (0001) planes are the two preferable planes during the GaN 3D growth.