III-nitride on silicon electrically injected microrings for nanophotonic circuits

Nanophotonic circuits using group III-nitrides on silicon are still lacking one key component: efficient electrical injection. In this paper we demonstrate an electrical injection scheme using a metal microbridge contact in thin III-nitride on silicon mushroom-type microrings that is compatible with integrated nanophotonic circuits with the goal of achieving electrically injected lasing. Using a central buried n-contact to bypass the insulating buffer layers, we are able to underetch the microring, which is essential for maintaining vertical confinement in a thin disk. We demonstrate direct current room-temperature electroluminescence with 440 mW/cm$^2$ output power density at 20 mA from such microrings with diameters of 30 to 50 $\mu$m. The first steps towards achieving an integrated photonic circuit are demonstrated.