MSM photodetector fabricated on polycrystalline silicon

Interdigitated metal-semiconductor-metal (MSM) photodetectors were fabricated by depositing metal contacts on top of a 2-μm-thick layer of polycrystalline silicon (polysilicon). These detectors have a -3-dB bandwidth of 750 MHz and a responsivity of 0.13 A/W at 860 nm. The bandwidth is more than twice that reported for conventional silicon MSM photodetectors as a result of the thin absorbing layer made possible by the higher optical absorption of polysilicon. A simple fabrication process that is compatible with standard VLSI processes, together with good performance characteristics, make this an ideal detector for integrated optoelectronic receivers for use in short distance, parallel optical data links.