N-face GaN films with hillock-free smooth surfaces grown by group-III-source flow-rate modulation epitaxy

Abstract

N-face GaN films were grown by group-III-source flow-rate modulation epitaxy (FME), wherein the flow-rate of group-III sources are sequentially modulated under a constant supply of NH3. By using GaN bulk substrates with a low misscut angle (∼0.3°), hillock-free N-face GaN surfaces are achieved over almost the whole sample area (10 × 5 mm2). A smooth surface with the root mean square roughness of 0.39 nm exhibits the step-and-terrace structure. Group-III-source FME also reduces carbon impurities in the films, resulting in weakened blue and yellow deep emissions in the photoluminescence spectrum.