Boron diffusion in amorphous silicon analized by SIMS and temperature dependent conductivity

Excellent surface passivation of heavily boron or phosphorus doped crystalline silicon is presented utilizing undoped hydrogenated amorphous silicon (a-Si:H). For passivating boron doped crystalline silicon surfaces, amorphous silicon needs to be deposited at low temperatures 150 °C≤Tdep≤200 °C, leading to a high bandgap. In contrast, low bandgap amorphous silicon causes an inferior surface passivation of highly boron doped crystalline silicon. Boron doping in crystalline silicon leads to a shift of the Fermi energy towards the valence band maximum in the undoped a-Si:H. A simulation, implementing dangling bond defects according to the defect pool model, shows this shift in the undoped a-Si:H passivation to be more pronounced if the a-Si:H has a lower bandgap. Hence, the inferior passivation of boron doped surfaces with low bandgap amorphous silicon stems from a lower silicon-hydrogen bond energy due to this shift of the Fermi energy. Hydrogen effusion and ellipsometry measurements support our interpretation.

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Effective p⁺-Doping of a-Si:H and a-Sic:H Layers by Plasma Assisted Boron Diffusion

Möhring

Bauer

Bilger

et al. 1986

MRS Proc.

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Doping of a-Si:H and a-SiC:H has been performed by plasma enhanced boron migration from thin (5–30 nm) Si0.2B0.8 layers on top of the substrate into the growing i-film. Transport coefficients for this plasma assisted diffusion (PAD) evaluated from SIMS profiles (D* = 10−15 … 10 cm2/s for a-Si:H, 10−15 cm2/s for a:SiC:H) by far exceed those for thermal diffusion after film deposition (10−21 cm2/s). Boron profiles are strongly governed by deposition parameters like substrate temperature, types and energies of radicals growing the film. Boron migration can be modelled assuming particle extraction from the network to the surface by bombardment of ions and atoms and high surface mobility of BHx radicals as a result from interaction with the plasma. Temperature dependent dark conductivity measurements show doping efficiencies comparable to B2H6 gas phase doping, but leaving plasma parameters optimized for i-film Leposition unchanged. Thin a-SiC:H layers are effectively p+-doped without affecting transmission, as no layer is optically detectable after PAD.

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Boron diffusion in amorphous silicon analized by SIMS and temperature dependent conductivity

Cited by 5 publications

References 5 publications

Boron diffusion in device-like B-doped a-SiC:H/a-Si:H heterojunction

Boron diffusion in device-like B-doped a-SiC:H/a-Si:H heterojunction

Surface passivation of heavily boron or phosphorus doped crystalline silicon utilizing amorphous silicon

Effective p⁺-Doping of a-Si:H and a-Sic:H Layers by Plasma Assisted Boron Diffusion

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Boron diffusion in amorphous silicon analized by SIMS and temperature dependent conductivity

Cited by 5 publications

References 5 publications

Boron diffusion in device-like B-doped a-SiC:H/a-Si:H heterojunction

Boron diffusion in device-like B-doped a-SiC:H/a-Si:H heterojunction

Surface passivation of heavily boron or phosphorus doped crystalline silicon utilizing amorphous silicon

Effective p+-Doping of a-Si:H and a-Sic:H Layers by Plasma Assisted Boron Diffusion

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Effective p⁺-Doping of a-Si:H and a-Sic:H Layers by Plasma Assisted Boron Diffusion