An ultra-high-speed vertically illuminated self-driven lateral asymmetric InSe photodetector

Two-dimensional (2D) materials have emerged as a promising platform for next-generation optoelectronic devices due to their unique electronic, optical, and mechanical properties, offering unprecedented opportunities for high-performance, low-power photodetection. We demonstrate a high-speed, zero-bias Au-InSe-multilayered graphene photodetector with an ultra-low dark current of 0.1 nA and photovoltaic-effect-driven photocurrent generation. The device exhibits a responsivity of 57.15 mA W^-1 and a detectivity of 1.58 × 10⁹ Jones at a wavelength of 785 nm. The device achieves an RF 3 dB bandwidth of 2.5 MHz, corresponding to an ultrafast response time of 140 ns, establishing a new benchmark for zero-bias InSe photodetectors. The exceptional performance is attributed to using asymmetric electrodes, which establish a built-in electric field within the depletion region. This field facilitates the rapid separation of photogenerated electron-hole pairs, which reduces carrier lifetime and minimizes recombination effects, thereby significantly boosting the response speed. Our results underscore the potential of InSe photodetectors with asymmetric contacts for achieving low dark current, high-speed operation, and low power consumption, offering a promising pathway for the development of next-generation optoelectronic devices based on 2D materials.