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Electric-field-assisted formation of an interfacial double-donor molecule in silicon nano-transistors.

Samanta A, Moraru D, Mizuno T, Tabe M - Sci Rep (2015)

Bottom Line: In this work, we identify pairs of donor atoms in the nano-channel of a silicon field-effect transistor and demonstrate merging of the donor-induced potential wells at the interface by applying vertical electric field.This is due to the decrease of the system's charging energy, as confirmed by Coulomb blockade simulations.These results represent the first experimental observation of electric-field-assisted formation of an interfacial double-donor molecule, opening a pathway for designing functional devices using multiple coupled dopant atoms.

View Article: PubMed Central - PubMed

Affiliation: Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8011, Japan.

ABSTRACT
Control of coupling of dopant atoms in silicon nanostructures is a fundamental challenge for dopant-based applications. However, it is difficult to find systems of only a few dopants that can be directly addressed and, therefore, experimental demonstration has not yet been obtained. In this work, we identify pairs of donor atoms in the nano-channel of a silicon field-effect transistor and demonstrate merging of the donor-induced potential wells at the interface by applying vertical electric field. This system can be described as an interfacial double-donor molecule. Single-electron tunneling current is used to probe the modification of the potential well. When merging occurs at the interface, the gate capacitance of the potential well suddenly increases, leading to an abrupt shift of the tunneling current peak to lower gate voltages. This is due to the decrease of the system's charging energy, as confirmed by Coulomb blockade simulations. These results represent the first experimental observation of electric-field-assisted formation of an interfacial double-donor molecule, opening a pathway for designing functional devices using multiple coupled dopant atoms.

No MeSH data available.


Ultrathin silicon-on-insulator field-effect transistors.(a) Schematic structure of an SOI-FET and its measurement setup. (b) A SEM image of a typical channel with dimensions below 100 nm. (c) TEM image of the channel taken across the channel width. (d) Schematic illustration of a possible arrangement of P-donors in a randomly, lower-concentration-doped channel. Under vertical electric field, potential wells can be formed at the interface. Neighboring potential wells may merge forming an interfacial double-donor molecule. (e) Schematic illustration of a possible distribution of P-donors in a selectively-doped higher-concentration channel. Clusters of several P-donors are located in the central region of the channel, strongly interacting to form multiple-donor QDs.
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f1: Ultrathin silicon-on-insulator field-effect transistors.(a) Schematic structure of an SOI-FET and its measurement setup. (b) A SEM image of a typical channel with dimensions below 100 nm. (c) TEM image of the channel taken across the channel width. (d) Schematic illustration of a possible arrangement of P-donors in a randomly, lower-concentration-doped channel. Under vertical electric field, potential wells can be formed at the interface. Neighboring potential wells may merge forming an interfacial double-donor molecule. (e) Schematic illustration of a possible distribution of P-donors in a selectively-doped higher-concentration channel. Clusters of several P-donors are located in the central region of the channel, strongly interacting to form multiple-donor QDs.

Mentions: A set of devices studied in this work are nano-channel silicon-on-insulator (SOI) MOSFETs, as illustrated in Fig. 1a. Channel length and width were modified as parameters in the ranges of 50–80 nm and 20–50 nm, respectively (details are described in Methods). Figure 1b shows a scanning electron microscope (SEM) image of the channel of one device with final width of ~40 nm and length of ~70 nm. The devices have an ultrathin Si channel (~5 nm), as observed from the cross-sectional transmission electron microscope (TEM) image shown in Fig. 1c. A 10-nm-thick SiO2 layer was thermally grown by dry oxidation as gate oxide, on top of which an Al frontgate was formed. The p-type Si substrate (boron-doped, NA ≈ 1 × 1016 cm−3) is used as a backgate through a 150-nm-thick buried oxide (BOX) layer. The frontgate and the backgate provide control of the electric field within the Si channel.


Electric-field-assisted formation of an interfacial double-donor molecule in silicon nano-transistors.

Samanta A, Moraru D, Mizuno T, Tabe M - Sci Rep (2015)

Ultrathin silicon-on-insulator field-effect transistors.(a) Schematic structure of an SOI-FET and its measurement setup. (b) A SEM image of a typical channel with dimensions below 100 nm. (c) TEM image of the channel taken across the channel width. (d) Schematic illustration of a possible arrangement of P-donors in a randomly, lower-concentration-doped channel. Under vertical electric field, potential wells can be formed at the interface. Neighboring potential wells may merge forming an interfacial double-donor molecule. (e) Schematic illustration of a possible distribution of P-donors in a selectively-doped higher-concentration channel. Clusters of several P-donors are located in the central region of the channel, strongly interacting to form multiple-donor QDs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663623&req=5

f1: Ultrathin silicon-on-insulator field-effect transistors.(a) Schematic structure of an SOI-FET and its measurement setup. (b) A SEM image of a typical channel with dimensions below 100 nm. (c) TEM image of the channel taken across the channel width. (d) Schematic illustration of a possible arrangement of P-donors in a randomly, lower-concentration-doped channel. Under vertical electric field, potential wells can be formed at the interface. Neighboring potential wells may merge forming an interfacial double-donor molecule. (e) Schematic illustration of a possible distribution of P-donors in a selectively-doped higher-concentration channel. Clusters of several P-donors are located in the central region of the channel, strongly interacting to form multiple-donor QDs.
Mentions: A set of devices studied in this work are nano-channel silicon-on-insulator (SOI) MOSFETs, as illustrated in Fig. 1a. Channel length and width were modified as parameters in the ranges of 50–80 nm and 20–50 nm, respectively (details are described in Methods). Figure 1b shows a scanning electron microscope (SEM) image of the channel of one device with final width of ~40 nm and length of ~70 nm. The devices have an ultrathin Si channel (~5 nm), as observed from the cross-sectional transmission electron microscope (TEM) image shown in Fig. 1c. A 10-nm-thick SiO2 layer was thermally grown by dry oxidation as gate oxide, on top of which an Al frontgate was formed. The p-type Si substrate (boron-doped, NA ≈ 1 × 1016 cm−3) is used as a backgate through a 150-nm-thick buried oxide (BOX) layer. The frontgate and the backgate provide control of the electric field within the Si channel.

Bottom Line: In this work, we identify pairs of donor atoms in the nano-channel of a silicon field-effect transistor and demonstrate merging of the donor-induced potential wells at the interface by applying vertical electric field.This is due to the decrease of the system's charging energy, as confirmed by Coulomb blockade simulations.These results represent the first experimental observation of electric-field-assisted formation of an interfacial double-donor molecule, opening a pathway for designing functional devices using multiple coupled dopant atoms.

View Article: PubMed Central - PubMed

Affiliation: Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8011, Japan.

ABSTRACT
Control of coupling of dopant atoms in silicon nanostructures is a fundamental challenge for dopant-based applications. However, it is difficult to find systems of only a few dopants that can be directly addressed and, therefore, experimental demonstration has not yet been obtained. In this work, we identify pairs of donor atoms in the nano-channel of a silicon field-effect transistor and demonstrate merging of the donor-induced potential wells at the interface by applying vertical electric field. This system can be described as an interfacial double-donor molecule. Single-electron tunneling current is used to probe the modification of the potential well. When merging occurs at the interface, the gate capacitance of the potential well suddenly increases, leading to an abrupt shift of the tunneling current peak to lower gate voltages. This is due to the decrease of the system's charging energy, as confirmed by Coulomb blockade simulations. These results represent the first experimental observation of electric-field-assisted formation of an interfacial double-donor molecule, opening a pathway for designing functional devices using multiple coupled dopant atoms.

No MeSH data available.