Bandwidth enhancement in silicon metal-semiconductor-metal photodetector by trench formation

We report on fabrication and characterization of a high-speed silicon metal-semiconductor-metal photodetector with novel structure. Metal contacts on the sidewalls of the interdigitated trenches are used to generate a highly uniform electric field well below the detector surface so that carriers deep within the semiconductor bulk can easily attain their saturation velocities. The detector, with 9-μm-deep interdigitated trenches and a trench spacing of 1 μm, has a pulse width of 28.2 ps and a -3-dB bandwidth of 2.2 GHz at 5 V. The responsivity measured at 790 nm is 0.14 A/W, corresponding to an external quantum efficiency of 22.1%. Our results also show that a bias as low as 2 V is sufficient for this diode to operate at high-speed without reducing responsivity.