Room-temperature 2-μm GeSn P-I-N homojunction light-emitting diode for inplane coupling to group-IV waveguides

We report the electroluminescence of a planar p-i-n diode based on an undoped GeSn layer where the p- and n-type electrodes are fabricated by using the CMOS process of ion implantation. The measurement shows a broad spectrum at a peak energy located below the bulk bandgap of Ge associated with indirect optical transition analyzed by taking into account composition- and strain-dependent modeling. This work provides an alternative approach to the fabrication of GeSn-based p-i-n light-emitting diodes as well as moving towards the integration with waveguided on-chip group IV photonic devices.