Highly responsive silicon-based hot-electron photodetector with self-aligned metamaterial interdigital electrodes

A sensitive silicon-based hot-electron photodetector based on a self-aligned metal–semiconductor–metal junction is developed. Nearly perfect absorption is achieved with the metamaterial optical coupling, whereas the absorption difference between the upper and lower interdigital gratings is as large as 70% near the resonant wavelength. Arising from the asymmetric photo-absorption, the measured responsivity values of the self-aligned interdigital grating devices reach 1.89 and 0.78 mA/W under zero biasing conditions at the wavelengths of 1310 and 1550 nm, respectively. These values approach the reported record photo-responsivity of hot-electron photodetectors with conventional metal–semiconductor junctions. In addition, the indication of polarity-switchable photocurrent appears due to the wavelength-dependent absorption of the upper and lower metal interdigital gratings. Our device, combining the self-aligned metamaterial interdigital electrodes with highly asymmetric absorption, shows prospects for applications in photodetection, photovoltaics, integrated optoelectronics, and optical communications.