Ge-on-Si photodetector with novel metallization schemes for on-chip optical interconnect

In this work, fabricated 1550-nm short-wavelength infrared (SWIR) Ge-on-Si photodetectors coupled with a Si waveguide on silicon-on-insulator (SOI) for on-chip optical interconnect as an energy-efficient green technology for next-generation very-large-scale integration (VLSI) systems are characterized. Here, a particular emphasis is put on the back-end-of-the-line (BEOL) technology in device design. Comparison study on the effects of interconnection geometry on the electrical and optical DC characteristics of the device is made. Compared with a reference device with bulk contacts, device with holey contacts demonstrated an increased optical responsivity. Further, device with holey contacts on two metal layers showed the highest photocurrent. Also, dependence of forward and reverse currents in the heterojunction pn diode on effective contact area is empirically studied. As a result, it is found that external quantum efficiency (EQE) can be significantly improved by engineering the geometry of metal interconnect in the Ge-on-Si photodetector without being affected by reduction in the effective contact area.