Defect-Engineered Electrically-Injected Germanium-on-Insulator Waveguide Light Emitters at Telecom Wavelengths

Ge-on-insulators (GOIs) have been extensively explored as a potential platform for electronic-photonic integrated circuits (EPICs), enabling various emerging applications. Although an efficient electrically-injected light source is highly desirable, realizing such devices with optimal light emission efficiency remains challenging. Here, the first room-temperature electrically-injected Ge waveguide light emitters consisting of a lateral p-i-n homojunction on a GOI platform that can be monolithically integrated with EPICs are demonstrated. A high-quality Ge active layer is transferred onto an insulator layer with the misfit dislocations in the Ge active layer eliminated to suppress unwanted nonradiative recombination. A 0.165% tensile strain is introduced to enhance the directness of the band structure and improve the light emission efficiency. The device comprises a waveguide structure with a significantly improved optical confinement as the optical resonator and a lateral p-i-n homojunction structure as the electrical injection structure. Under continuous-wave electrical current injection at room temperature, enhanced electroluminescence is successfully observed at telecommunications wavelengths covering the C, L, and U bands, with improved efficiency. Theoretical analysis suggests that the quantum efficiency of Ge light emitters is dramatically affected by the defect density. These results pave the way for developing efficient, room-temperature, electrically-injected light emitters for next-generation GOI-based EPICs.