Low-Threshold AlGaN-Based Multiple-Quantum-Well Laser on High-Temperature Annealed AlN Template

The influence of AlN templates with different threading dislocation densities (TDDs) on the lasing characteristics of edge-emitting AlGaN based multiple-quantum well (MQW) lasers were investigated. The regrown A1N film on high-temperature annealed sputtered AlN (Reg-HTA AlN) had a step flow surface morphology and 72.5% lower TDD than the in-situ grown AlN film by metal-organic chemical vapor deposition (MO AlN). The threshold power density of the deep ultraviolet lasing from the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Al}_{0.6}\text{Ga}_{0.4}\mathrm{N}/\text{AlN}$</tex> MQWs on the Reg-HTA AlN template was dramatically reduced to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$86 \ \text{kW}/\text{cm}^{2}$</tex>, which was 76.5% lower than that on the MO AlN template, and the linewidth after threshold was only 0.22 nm. The improved lasing performance was attributed to the reduced internal loss and enhanced radiation recombination rate in the MQWs on the Reg-HTA AlN template.