AlGaInN Violet Laser Diodes Grown on GaN Substrates with Low Aspect Ratio

AlGaInN violet laser diodes grown on GaN substrates have been studied. Waveguide simulations have been performed and perpendicular radiation angles have been investigated. A peculiar layer structure has been proposed to reduce the perpendicular radiation angle and compared with a conventional laser. The laser structure has an n-cladding layer consisting of three AlGaN films, the middle film of which has relatively high Al composition. A laser diode with an optimized structure has been fabricated. The threshold current density and slope efficiency have been 2.9 kA/cm2 and 1.4 W/A, respectively. The perpendicular radiation angle has been as small as 16.2°. The AlGaInN violet laser diode with a low aspect ratio of 1.6 and a small threshold current of 29 mA has been realized.