TERAHERTZ GAAS METAL-SEMICONDUCTOR-METAL PHOTODETECTORS WITH 25 NM FINGER SPACING AND FINGER WIDTH

We have fabricated metal-semiconductor-metal (MSM) photodetectors with the smallest finger spacing and finger width of 25 nm on molecular beam epitaxy grown GaAs. Direct current measurement shows that they have low dark current and high sensitivity. Monte Carlo simulations demonstrate that for a MSM photodetector with 25 nm finger spacing and width, the full width at half maximum impulse response is as short as 0.25 ps and the 3 dB bandwidth is 0.4 THz. They also show that by eliminating holes, the bandwidth can be over 1.8 THz. Furthermore, the detector capacitance was calculated, indicating that by reducing the ratio of finger width to finger spacing the detector capacitance can be decreased.