Reduction of the lasing threshold in optically pumped AlGaN/GaN lasers with two-step etched facets

We report a two-step process to obtain smooth and vertical {10-10} m-plane facets in AlGaN/GaN separate confinement heterostructures designed to fabricate ultraviolet lasers emitting at 355 nm. The process combines inductively coupled plasma reactive ion etching with crystallographic-selective wet etching using a KOH-based solution. The anisotropy in the wet etching allows the fabrication of flat, parallel facets without degradation of the multilayer ensemble. The optical performance of the lasers is strongly improved (reduction of the lasing threshold by a factor of two) when using the two-step process for the definition of the cavity, in comparison to cavities fabricated by mechanical cleaving.