2020 Fiscal Year Research-status Report
Study of two-dimensional Si Esaki diodes at ultra-high doping with semimetal behavior
| Project/Area Number |
19K04529
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| Research Institution | Shizuoka University |
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Principal Investigator |
Moraru Daniel 静岡大学, 電子工学研究所, 准教授 (60549715)
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| Project Period (FY) |
2019-04-01 – 2022-03-31
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| Keywords | Esaki diode / semimetal / donor-acceptor pair / band-to-band tunneling / silicon-on-insulator |
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| Outline of Annual Research Achievements |
The research aims to identify new properties of Si nanodevices doped with both donors and acceptors, in particular in terms of band-to-band tunneling (BTBT) transport in tunnel diodes doped at high doping concentrations.
Recently, we reported a surprising aspect of Si nanoscale pn junction diodes, doped with significantly lower doping concentrations. From electrical measurements, we showed that BTBT mechanism can also be found in such devices. This provides a new basis for understanding the BTBT mechanism in different regimes and structures (published in Jpn. J. Appl. Phys. 2021).
In parallel, we investigated by first-principles simulations properties of nanoscale counter-doped Si transistors. We reported electron transport mediated by donor clusters and potential-modulation effect of acceptors atoms (accepted for publication in Appl. Phys. Express 2021).
New devices have been fabricated for experimental measurements and the theoretical analysis is currently extended to transport in nanoscale pn diodes and the role of donor-acceptor pairs.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The research is progressing well, and new insights are obtained on different aspects of the project.
First, we demonstrated a surprising possibility of activating band-to-band tunneling (BTBT) transport in pn junction diodes even with lower doping concentrations. This basic finding was based on the experimental results of nanoscale pn (and pin) diodes analyzed at room temperature (published in Jpn. J. Appl. Phys. 2021).
Second, we succeeded in fabricating a first batch of pn and pin diodes using the rapid thermal annealing (RTA) technology for doping (newly installed, supported from this funding). The devices are currently under measurements.
Third, we proceeded significantly with our first-principles simulations, to demonstrate the role of counter-doping in Si nanoscale transistor operation (accepted for publication in Appl. Phys. Express). We are also addressing the Si nanoscale pn diodes as a main extension of this analysis.
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| Strategy for Future Research Activity |
The next research will be carried out based on the results obtained so far.
As a first target, we will clarify further, by first-principles simulations, the effect of donors and acceptors (focusing on a single-donor/single-acceptor pair) on band-to-band tunneling (BTBT) in Si pn nano-diodes. Extensive simulations are expected to provide fundamental insights on the role of donor-acceptor pairs in BTBT transport under various conditions.
As a second target, we will continue measurements on the new highly-doped pn (and pin) diodes, in particular at low temperature. Based on these results, new devices will be designed and fabricated, with a target of creating very abrupt highly-doped pn tunnel diodes.
Finally, as a third target, we will experimentally analyze counter-doped silicon-on-insulator nanoscale transistors. The goal is to clarify the impact of interactions between donors and acceptors for single-electron tunneling operation in such devices.
It is expected that the above analyses can help clarify the nature of highly doped (and counter-doped) Si nanoscale structures, including their "semimetal" behavior, and the impact on tunneling transport.
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