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 _0.7Ga _0.3N/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 μJ/cm ² was experimentally determined, corresponding to 1.4 × 10 ¹⁷cm ^-3 excited carriers. These findings pave the way for the demonstration of solid-state lasers with sub-250 nm emission at room temperature.