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.