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 NH
₄
OH), semiconductor doping, and annealing on the contact resistivity (rho
_c
) of Ti
_0.1
W
_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 NH
₄
OH before TiW contacts were deposited by blanket sputtering. InGaAs samples doped at 5 times 10
¹⁹
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-cm
²
. 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-cm
²
. TiW contacts on samples having same active dopants, with no UV-ozone oxidation and only 10 seconds of concentrated NH
₄
OH etch exhibit rho
_c
of (2.49 plusmn 0.40) plusmn 10
^-8
Omega-cm
²
.