Organo-arsenic Molecular Layers on Silicon for High-Density Doping

Abstract

This article describes for the first time the controlled monolayer doping (MLD) of bulk and nanostructured crystalline silicon with As at concentrations approaching 2 × 10 20 atoms cm −3 . Characterization of doped structures after the MLD process confirmed that they remained defect-and damage-free, with no indication of increased roughness or a change in morphology. Electrical characterization of the doped substrates and nanowire test structures allowed determination of resistivity, sheet resistance, and active doping levels. Extremely high As-doped Si substrates and nanowire devices could be obtained and controlled using specific capping and annealing steps. Significantly, the As-doped nanowires exhibited resistances several orders of magnitude lower than the predoped materials.

Chemical approaches for doping nanodevice architectures

“…Nevertheless, Long et al recently published a study on As-MLD of Ge. [45] The molecule previously utilised by O'Connell and co-workers [40] was used but was dissolved in IPA as opposed to mesitylene. As the hydrogermylation temperature of 200 ο C greatly exceeds the decomposition temperature of the TAA molecule, UV-initiated hydrogermylation was used.…”

Monolayer Doping of Si with Improved Oxidation Resistance

“…We have recently reported MLD on Si using a traditional carbon-based As-containing precursor in conjunction with a thermally-initiated hydrosilylation reaction and achieved excellent in-diffusion coupled with high chemical concentrations approaching 2 × 10 20 atoms/cm 3 . 45 The lower carrier concentration for arsenic observed in this work is unlikely due to diffusion suppression. Nitrogen has been reported to supress diffusion of As in Ge 51 and also suppression of B in Si 52 but has not been reported to suppress the diffusion of As in Si.…”

Monolayer functionalization of silicon micro and nanowires : towards solar-to-fuel and sensing devices

“…89 Even the 20 nm devices showed a proper current conduction, which indicates that the MLD process can be applied to small feature sizes as well. The resistivity of the nanowires was decreased by five orders of magnitude for nanowires with a width >40 nm and by seven orders of magnitude for smaller nanowires.…”

“…Conversely, the total amount of doping can be regulated upwards by the use of dopant-rich molecules, for example using carborane molecules that have 10 boron atoms per molecule, which resulted in surface concentrations of ~5 × 10 19 atoms/cm 3 . 88 The MLD method has been expanded to the use of arsenic atoms as n-type dopants using triallylarsine, 89 methylarsenic acid, 90 or arsenic azide by click chemistry. 91 Recently, the use of nitrogen-containing precursor molecules has also been reported, 92 since nitrogen atoms have a lower thermal diffusion coefficient than phosphorus or boron.…”