Ge n + /p shallow junctions for light emission and detection applications

Si-based light sources and photodetectors are the key active components for single chip integrated optoelectronic circuits. Ge and GeSn alloys can serve as channel material for high carrier mobility metal-oxide-semiconductor field effect transistors (MOSFET) and also be considered as the promising materials for efficient light emission and detection due to their quasi-direct band structure and compatibility with Si technology. [1] To improve light emitting efficiency of Ge, tensile strain and n-type heavy doping were applied for reduction of difference between direct and indirect band gap and improvement of electron occupation in Γ valley. However, it is difficult to achieve high activation n-type doping in Ge because of fast diffusion of n-type dopants and low dopant solid solubility in Ge.[2] In this work, Ge n + /p shallow junctions are fabricated with high n-type doping concentration by ion implantation and excimer laser annealing techniques, which can serve as source and drain in scaled Ge nMOSFET. Strong electroluminescence and high photoresponsivity from the Ge n + /p shallow junctions are demonstrated.