Record Low Contact Resistivity (4.4×10−10 Ω-cm2) to Ge Using In-situ B and Sn Incorporation by CVD With Low Thermal Budget (≤400°C) and Without Ga

The record low contact resistivity (ρ
_c
) of 4.4×10
^-10
Ω-cm
²
is achieved in Ti metal contact to in-situ B-doped GeSn using B and Sn segregations at the Ti/GeSn:B interface. Sn incorporation into Ge lowers the Schottky barrier height of holes. Increasing B doping at the Ti/GeSn:B interface reduces the hole tunneling distance. Thanks to the low growth temperature (305°C) of the chemical vapor deposition using Ge
₂
H
₆
, the GeSn:B with the bulk active [B] of solid solubility of B in Ge=5.5×10
¹⁸
cm
^-3
) and the bulk [Sn] of 4.9% is successfully grown. Without the needs of the previously reported Ga dopants and the high temperature annealing for dopant activation, the record low ρ
_c
is achieved with all the process temperatures ≤ 400
^o
C.