The results puplished under the title "An electrically pumped surface-emitting semiconductor green laser" in Science Advances detail an all-epitaxially grown device that exploits the photonic band edge modes formed in dislocation-free gallium nitride nanocrystal arrays, instead of using conventional distributed Bragg reflectors (DBRs).
So far, room temperature surface-emitting green laser diodes relied on dual dielectric distributed Bragg reflectors (DBRs) and water bonding to a copper plate for low thermal resistance, but such devices exhibited a very large threshold current density at room temperature, and their light emission was limited to 400 and 460nm (violet blue).
In contrast, the 10μm-diameter device operates at around 523nm and exhibits a threshold current of about 400A/cm2, over one order of magnitude lower compared to previously reported blue laser diodes. First explored through simulation, the so-called nanocrystal surface-emitting laser (NCSEL) was carefully engineered from InGaN/AlGaN (indium gallium nitride/aluminum gallium nitride) nanocrystal arrays of precisely controlled size, spacing and surface morphology.
The efficient strain relaxation in the conical core-shell InGaN/AlGaN multiple quantum disks within the nanowires ensured the nanostructures were free of dislocations.