Growth of Ga- and N- polar gallium nitride layers by metalorganic vapor phase epitaxy on sapphire wafers

Following an already established polarity control scheme for GaN thin films, we developed a process to simultaneously grow Ga- and N-polarity layers side by side on c-plane sapphire. The simultaneous growth is achieved by properly treating the AlN nucleation/buffer layer and subsequent substrate annealing. During this process, the growth is mass-transfer-limited, permitting the same growth rate for both types of polarity domains. Smooth domains of both polarity types (RMS roughness ∼1–2 nm) were obtained.