Ultrafast Metal-Semiconductor-Metal Photodetectors with Nanometer Scale Finger Spacing and Width

Abstract

We report the fabrication and measurement of ultrafast nanoscale metal-semiconductor-metal photodetectors. The finger spacing and width as small as 25 nm are fabricated using electron beam lithography. Electrooptic sampling was performed at various wavelengths to measure the detectors' response time. The fastest detectors have response times and 3-dB bandwidths of 0.87 ps and 510 GHz on low-temperature GaAs, 1.5 ps and 300 GHz on bulk GaAs, and 3.7 ps and 110 GHz on bulk Si. To our knowledge, they are the fastest photodetectors of their kind. Scaling rules are also proposed.