In situ ohmic contact formation for n-type Ge via non-equilibrium processing


In situ ohmic contact formation for n-type Ge via non-equilibrium processing

Prucnal, S.; Frigerio, J.; Napolitani, E.; Ballabio, A.; Berencén, Y.; Rebohle, L.; Wang, M.; Böttger, R.; Voelskow, M.; Isella, G.; Hübner, R.; Helm, M.; Zhou, S.; Skorupa, W.

Highly scaled nanoelectronics requires effective channel doping above 5×10^19 /cm3 together with ohmic contacts with extremely low specific contact resistivity. Nowadays, Ge becomes very attractive for modern optoelectronics due to the high carrier mobility and the quasi-direct bandgap, but n-type Ge doped above 5×10^19 /cm3 is metastable and thus difficult to be achieved. In this letter, we report on the formation of low-resistivity ohmic contacts in highly n-type doped Ge via non-equilibrium thermal processing consisting of millisecond-range flash lamp annealing. This is a single-step process that allows for the formation of a 90 nm thick NiGe layer with a very sharp interface between NiGe and Ge. The measured carrier concentration in Ge is above 9×10^19 /cm3 with a specific contact resistivity of 1.2×10^(−6) Ω cm2.
Simultaneously, both the diffusion and the electrical deactivation of P are fully suppressed.

Keywords: germanium; flash lamp annealing; ion implantation; NiGe; ohmic contact

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Publ.-Id: 26223