Germanium Metal-Semiconductor-Metal Photodetectors Evanescently Coupled With Upper-Level Silicon Oxynitride Dielectric Waveguides

We demonstrate Ge-on-Si metal-semiconductor-metal (MSM) photodetectors monolithically integrated with silicon oxynitride (SiOxNy) waveguides. The waveguide is placed on top of the photodetector and between the metal electrodes, evading the shading effect by metal electrodes, which is typical in surface-illuminated MSM photodetectors. The devices showed responsivity of about 0.45 A/W for 80 mu m long devices at 1550 nm. The photodetector with 1.5 mu m electrode spacing showed 3 dB bandwidth of 2.0 GHz at -2V and 2 mu A dark current. Further studies suggest that with a modified design the structure is capable of achieving 1 A/W responsivity and greater bandwidth. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773212]