Ultrafast nanoscale metal-semiconductor-metal photodetectors on bulk and low-temperature grown GaAs

Abstract

Metal-semiconductor-metal photodetectors of finger spacing and width as small as 100 nm have been fabricated on bulk and low-temperature grown GaAs, and tested using a femtosecond pulse laser and high-speed electro-optic sampling. The fastest photodetectors have a measured full width at half maximum impulse response and a 3-dB bandwidth of 0.87 ps and 510 GHz, respectively, for low-temperature grown GaAs limited by carrier recombination time; and of 1.5 ps and 295 GHz for bulk GaAs, limited by the RC time constant. To our knowledge, they are the fastest detectors of their kinds reported to date.