2019 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 |
This research aims to demonstrate that highly-doped silicon can exhibit properties of "semimetal". For that, we studied highly-doped silicon-on-insulator (SOI) tunnel (Esaki) diodes with depletion layer co-doped with phosphorus (P) donors and boron (B) acceptors at high concentrations. We reported, for the first time, single-charge band-to-band tunneling (SC-BTBT) at low temperatures. This has been supported by simulations suggesting that quantum dots are formed by clusters of non-compensated donors in the nanoscale depletion-layer.
We also reported the role of donor clusters for single-electron tunneling (SET) in selectively-doped SOI transistors. It was shown that the tunnel resistance modulation is critical, providing insights for high-temperature SET operation via dopant quantum dots.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
This research was organized in several parts.
First, new Esaki diodes have been fabricated in SOI substrates, with high concentrations. New designs of pn/pin diodes with gates have been implemented using thermal-diffusion doping. However, a rapid thermal processing (RTP) system has been purchased and installed this year and will be used for abrupt pn junctions.
Second, IV characterization of tunnel diodes and highly-doped transistors has been carried out. This revealed band-to-band tunneling via dopant-induced quantum dots in the nano-devices (Appl. Phys. Lett. 2019). This is a key milestone for demonstration of "semimetal" behavior of highly doped (co-doped) nanoscale Si.
Third, the properties of donor-acceptor pairs in nano-channels have been analyzed by first-principles simulations.
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| Strategy for Future Research Activity |
The next research will also be carried out in several parts.
First, IV characteristics will be measured for highly-doped pn Esaki diodes with gates. By controlling gate voltage, we expect to control single-charge band-to-band tunneling via dopant states. This mechanism can probe the properties of "semimetal" of highly-doped nanoscale-Si.
Second, rapid thermal processing (RTP) will be tested for design of abrupt pn junctions. This will allow the development of new fabrication for high-concentration abruptly-doped Esaki diodes.
Third, first-principles simulations will be used to study the interplay of donors and acceptors in co-doped nanoscale Si. The simulation results will be correlated with experimental measurements not only for Esaki diodes, but also for co-doped nanoscale Si transistors.
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