Enhancing the sub-bandgap photo-response of silicon by inert element co-hyperdoping.

The introduction of intermediate bands by hyperdoping is an efficient way to realize infrared light absorption of silicon. In this Letter, inert element (helium and argon for specific)-doped black silicon is obtained by helium ion-implantation followed by femtosecond pulse laser irradiation in an argon atmosphere based on near-intrinsic silicon substrates. Within the 200 nm of the silicon surface, the concentrations of helium and argon are both above the order of 10 cm. The defect states related to impurities and structural defects contribute to the absorption in sub-bandgap (1100-2500 nm). Vertically structured devices based on the inert element-doped black silicon exhibit the responsivity of 350 mA/W for 1550 nm and 165 mA/W for 1310 nm at 12 V operating bias, respectively, proving its potential application in infrared detection.