Comparison of Polished and Dry Etched Semipolar $(11\bar{2}2)$ III-Nitride Laser Facets

We compare facet morphology, device characteristics, and far field patterns (FFPs) for semipolar (112̅2) laser diodes fabricated with mechanically polished and dry etched mirror facets. Facets formed by Cl2-based dry etching produced inclined and heavily striated facets. Mechanically polished facets, in contrast, provided vertical and smooth facets (rms roughness=5.2 nm). The threshold currents of polished facet devices were on average ~ 100 and ~ 200 mA lower than etched facet devices (2 × 1200 μm² and 4 × 1200 μm² dimension devices, respectively). FFPs from etched facets were also shown to be obscured due to substrate reflections.