Challenges and breakthroughs in the development of AlGaN-based UVC lasers

Despite the rapid progress in III-nitride-based laser diodes, sub-300 nm UV semiconductors lasers have not been realized yet, mainly due to technical and scientific barriers arising from the lack of proper crystalline substrates and poor understanding of defect control in the wide bandgap semiconductors. In addition to low dislocation density, reduction in non-radiative centers and compensating point defect is required to achieve high internal quantum efficiency (IQE). AlGaN-based technology developed on single crystalline AlN substrates offers a pathway to address these challenges [1, 2]. Recently, UV LEDs emitting at 265 nm with output powers exceeding 80 mW and high reliability [3], as well as low-threshold, optically pumped lasers emitting at wavelengths between 230-280 nm [4,5] have been demonstrated.