Phosphorus atomic layer doping in Ge using RPCVD

Phosphorus atomic layer doping (P-ALD) in Ge is investigated at temperatures between 100 °C and 400 °C using a single wafer reduced pressure chemical vapor deposition (RPCVD) system. Hydrogen-terminated and hydrogen-free Ge (1 0 0) surfaces are exposed to PH3 at different PH3 partial pressures after interrupting Ge growth. The adsorption and reaction of PH3 proceed on a hydrogen-free Ge surface. For all temperatures and PH3 partial pressures used for the P-ALD, the P dose increased with increasing PH3 exposure time and saturated. The saturation value of the incorporated P dose at 300 °C is ∼1.5 × 1014 cm−3, which is close to a quarter of a monolayer of the Ge (1 0 0) surface. The P dose could be simulated assuming a Langmuir-type kinetics model with a saturation value of Nt = 1.55 × 1014 cm−2 (a quarter of a monolayer), reaction rate constant kr = 77 s−1 and thermal equilibrium constant K = 3.0 × 10−2 Pa−1. An electrically active P concentration of 5–6 × 1019 cm−3, which is a 5–6 times higher thermal solubility of P in Ge, is obtained by multiple P spike fabrication using the P-ALD process.

► Phosphorus (P) atomic layer doping (ALD) in Ge by CVD is investigated.
► Ge (1 0 0) surface is exposed to PH3 followed by Ge cap deposition.
► P adsorption is suppressed by hydrogen-termination of Ge surface.
► The adsorbed P increases with increasing PH3 exposure time and saturates.
► The P adsorption process is self-limited and follows Langmuir-type kinetics model.