Fabrication of sub-200 nm AlN-GaN-AlN waveguide with cleaved end facet

The authors report the first realization of sub-200 nm wide AlN-GaN-AlN (AGA) ridge waveguide with height-to-width ratio of ∼6:1, fabricated via inductively coupled plasma (ICP) etching with Cl₂/Ar gas chemistry. Reactive ion etching (RIE) power and ICP power were varied in the ranges of 100-450 W and 200-600 W, respectively. An optimized RIE power and ICP power at 100 and 400 W, respectively, reduced the density of nanorods formed in the etched trenches. Further optimization of the gas flow rate of Cl₂/Ar to 40/10 sccm improved the slope of the etched waveguide. In addition, the authors also developed a simple and novel dice-and-cleave technique to achieve cleaved end facet of AGA waveguide.