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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.


Calculation of probability of donor-well merging.(a,b) Number of isolated and merged dopant-induced wells calculated probabilistically as a function of electric field for two different distances of P-donors from the back interface: 3.8 nm [(a)] and 2.7 nm [(b)]. Insets: number of systems in the device channel containing 2, 3, or 4 merged P-donor wells assuming a Poisson distribution of the P-donors. The green zones correspond to the range of electric fields estimated for our experiment.
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f3: Calculation of probability of donor-well merging.(a,b) Number of isolated and merged dopant-induced wells calculated probabilistically as a function of electric field for two different distances of P-donors from the back interface: 3.8 nm [(a)] and 2.7 nm [(b)]. Insets: number of systems in the device channel containing 2, 3, or 4 merged P-donor wells assuming a Poisson distribution of the P-donors. The green zones correspond to the range of electric fields estimated for our experiment.

Mentions: where N is the total number of donors in the channel, r is the radius of the lateral confinement of the donor-induced well and V is the volume of the channel. The total number of donor atoms in the channel is ~14, as calculated from channel dimensions (70 × 40 × 5 nm3) and average doping concentration (ND = 1 × 1018 cm−3). After calculating the above probability, we can evaluate the number of donor-wells distributed as isolated and as merged. For instance, assuming that all donor atoms are situated at distance 3.8 nm from the Si/BOX interface, this evaluation leads to the results shown in Fig. 3a. This figure shows that the number of merged donor-wells gradually increases with increasing electric field. At the same time, the number of isolated donor-wells gradually decreases. Systems of merged donor-wells can be further classified as a function of the number of P-donors that are coupled together within a distance smaller than 2rB from each other. We calculate the probability of finding systems containing 2, 3, and 4 merged P-donor wells assuming a Poisson distribution of the donors in the lateral plane29. The basic result is shown as an inset in Fig. 3a. This result suggests that, for electric field of approximately 20–40 mV/nm (marked as a green zone in the inset), donor-well pairs (double-donor molecule-like systems) can be found in the channel. At the same time, the chance of finding higher-order merging of multiple P-donor wells is negligible.


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)

Calculation of probability of donor-well merging.(a,b) Number of isolated and merged dopant-induced wells calculated probabilistically as a function of electric field for two different distances of P-donors from the back interface: 3.8 nm [(a)] and 2.7 nm [(b)]. Insets: number of systems in the device channel containing 2, 3, or 4 merged P-donor wells assuming a Poisson distribution of the P-donors. The green zones correspond to the range of electric fields estimated for our experiment.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: Calculation of probability of donor-well merging.(a,b) Number of isolated and merged dopant-induced wells calculated probabilistically as a function of electric field for two different distances of P-donors from the back interface: 3.8 nm [(a)] and 2.7 nm [(b)]. Insets: number of systems in the device channel containing 2, 3, or 4 merged P-donor wells assuming a Poisson distribution of the P-donors. The green zones correspond to the range of electric fields estimated for our experiment.
Mentions: where N is the total number of donors in the channel, r is the radius of the lateral confinement of the donor-induced well and V is the volume of the channel. The total number of donor atoms in the channel is ~14, as calculated from channel dimensions (70 × 40 × 5 nm3) and average doping concentration (ND = 1 × 1018 cm−3). After calculating the above probability, we can evaluate the number of donor-wells distributed as isolated and as merged. For instance, assuming that all donor atoms are situated at distance 3.8 nm from the Si/BOX interface, this evaluation leads to the results shown in Fig. 3a. This figure shows that the number of merged donor-wells gradually increases with increasing electric field. At the same time, the number of isolated donor-wells gradually decreases. Systems of merged donor-wells can be further classified as a function of the number of P-donors that are coupled together within a distance smaller than 2rB from each other. We calculate the probability of finding systems containing 2, 3, and 4 merged P-donor wells assuming a Poisson distribution of the donors in the lateral plane29. The basic result is shown as an inset in Fig. 3a. This result suggests that, for electric field of approximately 20–40 mV/nm (marked as a green zone in the inset), donor-well pairs (double-donor molecule-like systems) can be found in the channel. At the same time, the chance of finding higher-order merging of multiple P-donor wells is negligible.

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.