Ultra-low specific contact resistivity (1.4 × 10~(-9) Ω·cm~2) for metal contacts on in-situ Ga-doped Ge_(0.95)Sn_(0.05) film

摘要

A heavily Ga-doped Ge_(0.95)Sn_(0.05) layer was grown on the Ge (100) substrate by molecular beam epitaxy (MBE), achieving an active doping concentration of 1.6 × 10~(20)cm~(-3) without the use of ion implantation and high temperature annealing that could cause Sn precipitation or surface segregation. An advanced nano-scale transfer length method was used to extract the specific contact resistivity ρ_c between the metal and the heavily doped p-Ge_(0.95_Sn_(0.05) layer. By incorporating Sn into Ge and in-situ Ga doping during the MBE growth, an ultra-low ρ_c of 1.4 × 10~(-9)Ω·cm~2 was achieved, which is 50% lower than the ρ_c of p~+-Ge control and is also the lowest value obtained for metal/p-type semiconductor contacts.