Sub-250 nm room-temperature optical gain from AlGaN/AlN multiple quantum wells with strong band-structure potential fluctuations

Deep-UV optical gain has been demonstrated in Al 0.7 Ga 0.3 N/AlN multiple quantum wells under femtosecond optical pumping. Samples were grown by molecular beam epitaxy under a growth mode that introduces band structure potential fluctuations and high-density nanocluster-like features within the AlGaN wells. A maximum net modal gain value of 118±9 cm −1 has been measured and the transparency threshold of 5±1 µ J/cm 2 was experimentally determined, corresponding to 1.4×10 17 cm −3 excited carriers. These findings pave the way for the demonstration of solid-state lasers with sub-250 nm emission at room temperature.