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 9.8x10(-8)cm(2) at 300 and 5.1x10(-8)cm(2) at 500 degrees C. Only 7nm 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.