Self-Aligned Ni-Germanide Ohmic Contact to n-Type GaAs Substrate for High Mobility III-V Channel Metal-Oxide Semiconductor Field-Effect Transistor (MOSFET)

We have investigated the microstructural evolution and electrical property of self-aligned Ni-germanide thin film formed on n-type GaAs (100) substrate as a function of rapid thermal annealing at temperatures in the range of 300 – 600 °C. The heteroepitaxial growth of Ge on GaAs (100) substrates was carried out using rapid thermal chemical vapor deposition (RTCVD) method. The Ge epitaxial layers were formed by the decomposition of GeH₄ in a H₂ ambient at substrate temperatures of 400 – 500 °C. The specific contact resistivity was extracted using four-point (Kelvin) probe technique. The specific contact resistivity values of the Ni-germanide films varied with variation in annealing temperature and were comparable to those obtained for Ni-germanide. A low specific contact resistivity of the order of 2.1 × 10^-6 Ωcm² was obtained for the Ni-germanide film formed at annealing temperature of 500 °C. The variation in the specific contact resistivity with annealing temperature could be associated with the phase evolution, surface and interface morphologies of Ni-germanide that occur at different annealing temperatures.