Ultralow Contact Resistivity on Ga-Doped Ge with Contact Co-Implantation of Ge and B

In this work, a comparative study of Ga, Ge+B, and Ga+B ion-implantation (I/I) is reported to improve the specific contact resistivity (rho (c)) on p-type Ge. It is found that Ga I/I shows superiority for shallow source/drain (S/D) junctions doping over Ge+B I/I and Ga+B I/I in terms of activation (N-a), junction depth (X-j), and rho (c); whereas for contact surface doping, Ge+B I/I and Ga+B I/I demonstrate advantage over Ga I/I owing to less dose loss in NiGe and more robust B segregation at the NiGe/Ge interface. Using a combination of Ga I/I and Ge+B I/I for shallow S/D junctions and contact surface doping respectively, an ultralow rho (c) of 2.7 x 10(-9) omega-cm(2) is achieved on p-type Ge.