Sub-band gap infrared absorption in Si implanted with Mg

Single-crystalline Mg-implanted Si layers are synthesized by ion implantation followed by pulsed laser melting. The Mg doping concentration is reaching 10²¹ cm⁻³. The Raman, Rutherford backscattering spectrometry/channeling and particle induced x-ray emission measurements confirm the recrystallization of the Mg-implanted Si layer. A strong below band gap infrared absorption over the wavelength range of 1.4–6.2 µm (0.2–0.87 eV, in the mid-infrared range) has been observed in the Mg-implanted Si layers. It is associated with deep levels induced by Mg atoms at high implantation level. This work points out the potential of Mg-implanted Si for room-temperature light detection in a broad infrared range for the new generation of Si-based photonics.