Enhancement of silicon sub-bandgap photodetection by helium-ion implantation.

Silicon sub-bandgap photodetectors can detect light at the infrared telecommunication wavelengths but with relatively weak photo-response. In this work, we demonstrate the enhancement of sub-bandgap photodetection in silicon by helium-ion implantation, without affecting the transparency that is an important beneficial feature of this type of photodetectors. With an implantation dose of 1 × 10¹³ ions/cm², the minimal detectable optical power can be improved from - 33.2 to - 63.1 dBm, or, by 29.9 dB, at the wavelength of 1550 nm, and the photo-response at the same optical power (- 10 dBm) can be enhanced by approximately 18.8 dB. Our work provides a method for strategically modifying the intrinsic trade-off between transparency and strong photo-responses of this type of photodetectors.