In Situ Site-Specific Gallium Filling and Nanograin Growth for Blocking of Threading Defects in Semipolar (1122) GaN

Undesirable nonuniformly distributed defects and mixed (1̅103) and (112̅2) phases during the growth of semipolar GaN films on m-plane sapphire substrates have been known to exist. In our study, we developed an interface-modification technique to achieve in situ site-specific Ga filling, nucleation, and nanograin growth, which efficiently blocked threading defects there. We have identified the mechanism governing the site-specific Ga filling and nanograin growth into Ga-rich islands based on surface atomic structures and theories of Gibbs free energy. Using the interface modification, we have achieved high-quality semipolar (112̅2) GaN films that enjoy merits of a very low basal-plane stacking fault density of ∼9 × 103 cm–1, a low threading dislocation density of ∼9 × 107 cm–2, and the strong band-edge-emission-dominated luminescence.