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 Ωcm² at 300 and 5.1 × 10⁻⁸ Ωcm² 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.