FABRICATION OF SUB-50 NM FINGER SPACING AND WIDTH HIGH-SPEED METAL-SEMICONDUCTOR-METAL PHOTODETECTORS USING HIGH-RESOLUTION ELECTRON-BEAM LITHOGRAPHY AND MOLECULAR-BEAM EPITAXY

Using high-resolution electron beam lithography, we have fabricated metal-semiconductor-metal photodetectors with sub-50 nm finger spacing and finger width on GaAs grown by molecular beam epitaxy, which are, to our knowledge, the smallest ever reported. Direct-current measurements showed that they have low dark current and high sensitivity. Proper scaling of the detectors to reduce the finger resistance and detector capacitance and to increase detector speed was studied. The resistances of thin metal lines with various widths were measured and compared with the value calculated from resistivity for bulk metal. Monte Carlo simulation demonstrates that for the photodetectors with 30 nm finger spacing and width, the response time is below picosecond and the cut-off frequency is over 1 THz.