Light Detection and Emission in Germanium-on-Insulator Diodes

We fabricated a germanium-on-insulator (GeOI) lateral p--i--n diode by a standard silicon process and characterized it as a photodetector and a light emitter. For the photodetector, we observed photosensitivity by an excitation light with the wavelength of 1550 nm. The experimental radio frequency response has completely agreed with simulated results, and the observed 3-dB bandwidth of 2 GHz was limited by contact resistances. For the light emitter, the electroluminescence spectra have broad peaks located at 1460 nm, much shorter than that of photoluminescence spectra located at 1600 nm. The difference was presumably attributable to the poor interface properties by the surface passivation. From these results, GeOI p--i--n diodes can be promising device candidates for silicon photonics by improving process conditions.