InGaN/GaN Quantum Dot Red $(\lambda=630~{\rm nm})$ Laser

Lasers emitting in the 600 nm wavelength range have gained attention for a number of important applications, including optical information processing, plastic fiber communication systems, optical storage, and full color (RGB) laser displays and laser projectors. Visible lasers are currently realized with GaN-based heterostructures having InGaN/GaN quantum wells as the gain media. The performance of these devices, particularly at longer wavelengths, is limited by materials inhomogeneity and effects related to a large strain-induced polarization in the quantum wells. A laser emitting in the red $(\lambda\sim 630~{\rm nm})$ has not been realized. Here, we demonstrate lasers which emit at 630 nm, the longest wavelength achieved with the nitride system, by incorporating InGaN/GaN self-organized quantum dots as the gain media. Strain relaxation during dot formation results in reduced polarization fields and consequently low threshold current density, ${\rm J}_{\rm th}=2.5~{\rm kA}/{\rm cm}^{2}$, small blue shift of the emission peak, very weak temperature dependence of ${\rm J}_{\rm th}~({\rm T}_{0}=236~{\rm K})$, and linearly TE polarized output.