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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.


Transport mechanism and Coulomb blockade simulation of merging donor-wells.(a) Schematic representation of the evolution of one main current peak (P1) with increasing VBG. P′1 corresponds to a fine current trace due to a satellite neighboring P-donor. Insets: potential landscapes of a double-donor system (with donors located at 3.8 nm and 4.5 nm, respectively, from the back interface) for different vertical electric fields (Fz). Three different regimes are shown: (i) Fz = 0 mV/nm; (ii) Fz–low; (iii) Fz–high. (b) Equivalent circuit of two parallel-coupled donor-induced QDs. (c) Equivalent circuit of two parallel-coupled donor-well QDs with increasing gate capacitance due to the gradual expansion of the donor-wells at the interface. (d) Equivalent circuit of merged two-donor-well (forming a single QD with larger gate capacitance). (e) Simulated IDS plotted in the VFG-VBG plane, as obtained for the sequence of equivalent circuits shown in (b–d).
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f5: Transport mechanism and Coulomb blockade simulation of merging donor-wells.(a) Schematic representation of the evolution of one main current peak (P1) with increasing VBG. P′1 corresponds to a fine current trace due to a satellite neighboring P-donor. Insets: potential landscapes of a double-donor system (with donors located at 3.8 nm and 4.5 nm, respectively, from the back interface) for different vertical electric fields (Fz). Three different regimes are shown: (i) Fz = 0 mV/nm; (ii) Fz–low; (iii) Fz–high. (b) Equivalent circuit of two parallel-coupled donor-induced QDs. (c) Equivalent circuit of two parallel-coupled donor-well QDs with increasing gate capacitance due to the gradual expansion of the donor-wells at the interface. (d) Equivalent circuit of merged two-donor-well (forming a single QD with larger gate capacitance). (e) Simulated IDS plotted in the VFG-VBG plane, as obtained for the sequence of equivalent circuits shown in (b–d).

Mentions: The main experimental observations for device B with lower doping concentration are schematically summarized in Fig. 5a. The key finding is the sudden shift of the current peak to lower VFG as VBG is increased. As suggested earlier, this shift could be related to the merging of neighboring P-donor wells, a phenomenon which can occur with relatively high probability in the lower-concentration devices. Within this model, the electron wave function is first gradually shifted from the main transport-donor (P1) toward the interface and then it abruptly expands due to merging with a neighboring P-donor (P′1) well. This satellite donor is expected to be energetically and spatially close to the main transport-donor, but it gives rise to a lower-intensity current possibly because of higher tunnel resistances.


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)

Transport mechanism and Coulomb blockade simulation of merging donor-wells.(a) Schematic representation of the evolution of one main current peak (P1) with increasing VBG. P′1 corresponds to a fine current trace due to a satellite neighboring P-donor. Insets: potential landscapes of a double-donor system (with donors located at 3.8 nm and 4.5 nm, respectively, from the back interface) for different vertical electric fields (Fz). Three different regimes are shown: (i) Fz = 0 mV/nm; (ii) Fz–low; (iii) Fz–high. (b) Equivalent circuit of two parallel-coupled donor-induced QDs. (c) Equivalent circuit of two parallel-coupled donor-well QDs with increasing gate capacitance due to the gradual expansion of the donor-wells at the interface. (d) Equivalent circuit of merged two-donor-well (forming a single QD with larger gate capacitance). (e) Simulated IDS plotted in the VFG-VBG plane, as obtained for the sequence of equivalent circuits shown in (b–d).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5: Transport mechanism and Coulomb blockade simulation of merging donor-wells.(a) Schematic representation of the evolution of one main current peak (P1) with increasing VBG. P′1 corresponds to a fine current trace due to a satellite neighboring P-donor. Insets: potential landscapes of a double-donor system (with donors located at 3.8 nm and 4.5 nm, respectively, from the back interface) for different vertical electric fields (Fz). Three different regimes are shown: (i) Fz = 0 mV/nm; (ii) Fz–low; (iii) Fz–high. (b) Equivalent circuit of two parallel-coupled donor-induced QDs. (c) Equivalent circuit of two parallel-coupled donor-well QDs with increasing gate capacitance due to the gradual expansion of the donor-wells at the interface. (d) Equivalent circuit of merged two-donor-well (forming a single QD with larger gate capacitance). (e) Simulated IDS plotted in the VFG-VBG plane, as obtained for the sequence of equivalent circuits shown in (b–d).
Mentions: The main experimental observations for device B with lower doping concentration are schematically summarized in Fig. 5a. The key finding is the sudden shift of the current peak to lower VFG as VBG is increased. As suggested earlier, this shift could be related to the merging of neighboring P-donor wells, a phenomenon which can occur with relatively high probability in the lower-concentration devices. Within this model, the electron wave function is first gradually shifted from the main transport-donor (P1) toward the interface and then it abruptly expands due to merging with a neighboring P-donor (P′1) well. This satellite donor is expected to be energetically and spatially close to the main transport-donor, but it gives rise to a lower-intensity current possibly because of higher tunnel resistances.

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.