Planar GeSn photodiode for high-detectivity photodetection at 1550 nm

We report an investigation of a planar GeSn p–i–n diode for a high-detectivity photodetector based on an undoped GeSn film. By fabricating n- and p-type regions on the plane of the GeSn film using the complementary metal–oxide–semiconductor technology of ion implantation, a low dark current density is revealed and attributed to the low defect density of the film and current flow suppression around the diode periphery. This yields a specific 1550-nm detectivity of ∼1010 cm Hz1/2 W−1, an order of magnitude higher than that of conventional vertical GeSn-based diodes and comparable to that of commercially available Ge-based diodes. This work provides an alternative approach for achieving a high-detectivity GeSn photodetector that may facilitate its potential applications.