Au‐free Si MOS compatible Ni/Ge/Al ohmic contacts to n⁺‐InGaAs

Complementary metal‐oxide semiconductor‐compatible Ni/Ge/Al ohmic contacts to a n + ‐InGaAs layer exhibited a specific contact resistivity of 9.8 × 10 −8 Ωcm 2 at 300 and 5.1 × 10 −8 Ωcm 2 at 500 °C. Only 7 nm of the n + ‐InGaAs layer was consumed during the Ni/Ge/Al ohmic formation. For comparison, Ni/Al and Ge/Ni/Al contacts showed a higher specific contact resistivity with significant consumption of the n + ‐InGaAs layer. The relatively low contact resistivities for Ni/Ge/Al are attributed to the transient increase in the donor concentration of n + ‐InGaAs. Ge metals segregated towards the n + ‐InGaAs surface and redistributed into the Ga and In sites, which increased the doping and acted as a diffusion barrier. These electrical and physical analyses of Ni/Ge/Al ohmic contacts to n + ‐InGaAs advance Au‐free metallization techniques for highly scaled InGaAs channel metal‐oxide field‐effect transistors.