Nitride-based quantum dot visible lasers

Blue- and green-emitting laser heterostructures are grown by molecular beam epitaxy, incorporating InGaN/GaN quantum dots as the active medium. The quantum dot growth parameters are optimized to obtain the highest photoluminescence (PL) intensity and radiative efficiency. Injected carrier lifetimes in the quantum dots are measured by temperature-dependent and time-resolved PL measurements. The blue lasers (λ = 479 nm) are characterized by threshold current densities of 1.8 kA cm−2 and 2.3 kA cm−2 under quasi-continuous wave bias for devices with Al0.08Ga0.92N and GaN waveguide cladding layers, respectively. The differential gain of these devices is 1.03 × 10−16 cm−2. A threshold current density of ∼1.65 kA cm−2 is measured for a green laser (λ = 545 nm) with Al0.08Ga0.92N cladding under quasi-continuous wave bias. (paper)