Surface Ga-Boosted Boron-Doped Si0.5 Ge0.5 using In-Situ CVD Epitaxy: Achieving 1.1 × 1021 cm−3 Active Doping Concentration and 5.7× 10−10 Ω-cm2 Contact Resistivity

For the first time, we have achieved contact resistivity (pc) less than 10
^-9
Ω-cm
²
for p-type metal/Si
_1-x
Ge
_x
contacts with in-situ doping-only technique. This is enabled by an optimized surface Gallium (Ga)-boosted Boron (B)-doped Si0.5Ge0.5 having active doping concentration (Na) of 1.1 ×10
²¹
cm
^-3
grown using reduced pressure chemical vapour deposition (RPCVD). Compared with B-only doped sample with Na of 9×10
²⁰
cm
^-3
B and Ga codoping enhances Na by 2×10
²⁰
cm
^-3
reducing ρc from 1.5×10
^-9
Ω-cm
²
to 5.7 ×10
¹⁰
Ω-cm
²
. ρc was extracted using advanced ladder transmission line model (LTLM) structures. It was also found that sub- 10
⁹
Ω-cm
²
ρ
_c
of our Ti/Si
_0.5
Ge
_0.5
contact can be maintained with thermal budget up to 450°C.