NiGe/n+-Ge junctions with ultralow contact resistivity formed by two-step P-ion implantation

Abstract

NiGe/n+-Ge junctions with low contact resistivity (ρC) were fabricated on p-Ge(100) substrates for Ge n-channel metal–oxide–semiconductor field-effect transistors by two-step P-ion implantation (P-I/I). The first P-I/I, followed by high-temperature annealing, was used to form an n+-Ge/p-Ge junction corresponding to the source/drain. The second P-I/I was used to form a NiGe/n+-Ge interface with high P concentration for metal contacts on the source/drain without high-temperature annealing to suppress the diffusion of P. ρC for the NiGe/n+-Ge was ∼3 × 10−8 Ω cm2, which is three orders of magnitude less than that for a conventional NiGe/n+-Ge formed without the second P-I/I, while maintaining the reverse-current level of conventional n+/p junctions.