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 ( ρ 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 ρ 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 ρ c of 2.7 × 10 −9 Ω-cm 2 is achieved on p-type Ge.