Electrically Injected Mid-Infrared GeSn Laser on Si Operating at 140 K

Abstract

Owing to its true direct bandgap and tunable bandgap energies, GeSn alloys are increasingly attractive as gain media for mid-IR lasers that can be monolithically integrated on Si. Demonstrations of optically pumped GeSn laser operating at room temperature under pulsed excitation and at cryogenic temperature under continuous-wave excitation show great promise of GeSn lasers to be efficient electrically injected light sources on Si. Here we report electrically injected GeSn lasers using Fabry-Perot cavity with 20 μm, 40 μm, and 80 μm ridge widths. A lasing threshold of 0.756 kA/cm ² at 77 K, emitting wavelength of 2722 nm, and maximum operating temperature of 140 K were obtained. The lower threshold current density compared to previous works was achieved by reducing optical loss and improving the optical confinement. The peak power was measured as 2.2 mW/facet at 77 K.