Effect of surface preparations on contact resistivity of TiW to highly doped n-InGaAs

We report the effects of UV-ozone oxidation, oxide removal etch chemistry (dilute HCl or concentrated NH₄OH), semiconductor doping, and annealing on the contact resistivity (rho_c) of Ti_0.1W_0.9 refractory alloy to n-type InGaAs. The semiconductor surface was oxidized through exposure to UV-ozone, then subsequently etched by either dilute HCl or concentrated NH₄OH before TiW contacts were deposited by blanket sputtering. InGaAs samples doped at 5 times 10¹⁹ cm^-3, treated with 10 minutes of UV-Ozone then one minute dilute HCl exhibited rho_c of (1.90 plusmn 0.35) times 10^-8 Omega-cm². The contacts are thermally stable at least to 400 degC where after one minute anneal, rho_c reduced to (1.29 plusmn 0.28) times 10^-8 Omega-cm². TiW contacts on samples having same active dopants, with no UV-ozone oxidation and only 10 seconds of concentrated NH₄OH etch exhibit rho_c of (2.49 plusmn 0.40) plusmn 10^-8 Omega-cm².