Spin-on doping of phosphorus on Ge with a 9 nm amorphous Si capping layer to achieve n +/ p   shallow junctions through rapid thermal annealing

In this paper, the Ge surface deterioration after spin-on doping (SOD) of phosphorus (P), (which suffers from moisture etch at high temperature) was effectively alleviated with a 9 nm amorphous Si (a-Si) capping layer (CL). The 9 nm a-Si CL, which will be oxidized and diffused into Ge, can effectively isolate the Ge surface from water vapour leading to insensitivity of the SOD process to the ambient humidity. Due to introduction of Si atoms, the diffusivity of P was greatly retarded. After a drive-in process by rapid thermal annealing (RTA) at 800°C for 1 min, a Ge-rich GeSi n +/ p shallow junctions were obtained with a junction depth of 40 nm. A rectification ratio of ~10 5 was achieved with an electrical activation energy of 0.64 eV for the n +/ p diode. These good performances suggest that this technique has great potential for n -type doping in Ge.