Epitaxial growth strategies and recent progress enabling room-temperature continuous-wave operation of AlGaN-based UV-B laser diodes

We present recent advancements in AlGaN-based UV-B laser diodes with a focus on epitaxial growth strategies to enhance device performance. While high-temperature (>1000℃) processes have traditionally been employed to achieve high-quality AlGaN, our findings indicate that such conditions degrade the sharpness of heterointerfaces critical to laser efficiency. By reducing the growth temperature to 750°C, we successfully suppressed Al content interdiffusion, leading to significantly improved interface steepness. This enabled enhanced carrier injection efficiency exceeding 50%, reduced spectral linewidths, and lower lasing thresholds. Furthermore, we achieved an output power of over 500 mW and wall-plug efficiency up to 2.9%, demonstrating the promise of low-temperature-grown AlGaN lasers for high-performance applications. Our results support a paradigm shift in AlGaN epitaxy, highlighting the necessity of precise thermal management during and after growth to realize high-efficiency UV-B laser diodes.