Continuous-Wave Electrically-Pumped MBE-Grown AlGaN UV-A Lasers with Tunnel Junctions

This work reports the first demonstration of continuous-wave (CW), electrically-pumped AlGaN ultraviolet-A (UV-A) laser diodes grown monolithically by plasma-assisted molecular beam epitaxy (PAMBE). To address the limitations associated with poor hole injection and high optical losses in conventional designs, our laser structure incorporates a transparent tunnel junction, enablingn-type top cladding for enhanced current spreading and low-resistance ohmic contacts. An index-guided narrow-ridge waveguide and an engineered cavity improve both lateral and transverse confinement and reduce optical losses within the laser resonator. The devices exhibit lasing at 360.3 nm at room temperature with a record-low threshold current density of 6 kA/cm² at a voltage drop of as low as 8.6 V. Our results mark a significant advancement in UV laser development, promising to realize high-performance PAMBE-grown AlGaN UV-A lasers.