Asymmetrically contacted germanium photodiode using a metal-interlayer-semiconductor-metal structure for extremely large dark current suppression.

In this study, we proposed germanium (Ge) metal-interlayer-semiconductor-metal (MISM) photodiodes (PD), with an anode of a metal-interlayer-semiconductor (MIS) contact and a cathode of a metal-semiconductor (MS) contact, to efficiently suppress the dark current of Ge PD. We selected titanium dioxide (TiO) as an interlayer material for the MIS contact, due to its large valence band offset and negative conduction band offset to Ge. We significantly suppress the dark current of Ge PD by introducing the MISM structure with a TiO interlayer, as this enhances the hole Schottky barrier height, and thus acts as a large barrier for holes.