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.