Research Topics

[Lectures　[Research Topics
[Equipments　[Publications　[Collaboration
[links　[ C V　[TOP

　　― Fabrication and Characterization of Quantum Nanostructures―
　　― Qubit (Quantum Bit)―
　　― (Quantum) Observation of Quantum States ―

We investigate the new device technology which enables quantum information handling by quantum mechanical switching of electronic devices, such as quantum dot(QD) transistors (Related Papers #1). A quantum dot FET structure, consisting of HEMT and self-assembled quantum dots, can be grown by Molecular Beam Epitaxy (MBE). Electronic states in a QD can be controlled by terminal voltage of the transistor (Fig.1a,b). It can be applied to spin FETs which detect spin states in the QDs , if combined with spin injection technology. (Topics-２) We are trying to build a semiconductor qubit structure based on these method.

＜Related Papers (Published)　
1. Kanji Yoh and Hironobu Kazama, and Yoshito Katano "A Quantum Dot FET―A Future Playground of Quantum State Manipulation - ," 59th Device Research Conference, Conference Digest pp.93-94 (2001).
IEEE Catalog Number:01TH8561 ISBN:0-7803-7014-7 Library of Congress:01-087536
2. Kanji Yoh and Hironobu Kazama, "Conductance Spectroscopy of InAs Quantum dots Buried in GaAs," Physica E, 7, pp.440-443 (2000).
3. Kanji Yoh and Sanshiro Shiina, "Crossover from Coulomb blockade to single electron memory mode in a d-dopedchannel GaAs split-gate transistor embedded with InAs dots in adjacent to the channel," The Physics of Semiconductors (World Scientific 1999).
＜Related Project
JST(Japan Science and Technology Corporation,　CREST (Core Research for Evolutional Science and Technology) " Development of Elemental Technology for Quantum Information Processing," Principal Investigator　Professor Shunichi Mutoh
＜Related Research in Other Groups
　Quantum Zeno Effect（Waseda University, Ohba/Nakazato Lab）　
　Tarucha ERATO Project (University of Tokyo, Professor Tarucha�s group)　
　List of Research Groups Working on Non-equilibrium Systems

To the top of the page

　　－Control of ferromagnetic metal/semiconductor interface－
　　－Polarization measurement of electroluminescence by spin injection －
　　－Spin-injection transistors－　

We are investigating spin transport, especially spin injection into semiconductors as well as spin transport in semiconductors. Our goal is to control spins electrically and eventually achieve the spin transistor operation. One of the challenging topics is the �spin injection� into semiconductors. We are pursuing the spin injection at ferromagnetic metal and semiconductor junctions in collaboration with Nanoelectronics group at our university (Prof.Mukasa), and Professor Ploog�s group (PDI in Berlin) Fig.2. Crystal growth (Fe on InAs for example) and injection measurement technology are the major key factors to achieve correct evaluation of spin injection. We have obtained satisfactory results so far. By combining this resul, we are hoping to achieve semiconductor based quantum computers. We are also pursuing spin-orbit interaction in 2DEG in narrow-gap semiconductors, and tunneling spectroscopy spin-dependent density of states at the surface inversion layer.

＜Related Papers (Published)
1. Hiroshi Ohno, Kanji Yoh, Toshihiro Doi, Agus Spagyo, Kazuhisa Sueoka, and Koichi Mukasa, "Spin injection with Fe/InAs hybrid structures,
" Int.Phys.Conf.Ser., No.170, Chapter 3, (2002) pp.275-280
2. Hiroshi Ohno, Kanji Yoh, Toshihiro Doi, Agus Spagyo, Kazuhisa Sueoka, and Koichi Mukasa, "Growth and Characterization of Fe(100)/InAs(100) hybrid structures," J.Vac.Sci. Technol.B.vol.19, Number 6, (2001) pp. 2280- 2283.
＜Related Projects
JST(Japan Science and Technology Corporation,　CREST (Core Research for Evolutional Science and Technology) " Development of Elemental Technology for Quantum Information Processing," Principal Investigator" Professor Shunichi Mutoh

To the top of the page

　― Ultra High Speed, Ultra Low Power Device―
　― Integration of Resonant Tunnel Diode with Advanced CMOS Technology―
　― Gigabit Technology based on Quantum Dot Unit Cell―

We investigate the giga-bit scale integration, ultra-high speed, low-power technology by pursuing conceptually new approaches. These attempts include new logic operation embedding non-linear device elements such as RTD or delay element into advanced CMOS technology. Ultimate goal is to turn the array of quantum dots into an array of logic gates by adding memory and logic function to each dot by one way or another. Anyhow, concept of non-linear systems and non-equilibrium systems are anticipated to play an important role.

＜Related Papers
Following are some of our early attempts for high speed, low power, new functional devices.
#1 deals with high performance MOSFET by introducing bipolar action in MOSFETs achieving 3 - 4 times enhancement in gm.
#2 reports high performance HEMTs in pure InAs channel FET structures.
#3 reports first attempt to combine FET with RTD and integrate them monolithically achieving new functional operation with high noise margin.
#4 reports the lowest speed�power product in semiconductors (in 1887) by monolithically integrating high performance strained InGaAs HEMTs and double heterojunction p-HEMTs.
1. Kanji Yoh, Ryouji Koizumi, Naotaka Hashimoto and Shuji Ikeda, "A High Performance p-Channel Transistor:b-MOSFET," Jpn.J.Appl.Phys, Vol.35, pp.906-909 (1996)
2. K.Yoh, T.Moriuchi and M.Inoue, "An InAs Channel Heterojunction Field-Effect Transistor with High Transconductance," IEEE Electron Device Lett., EDL-11(11), pp593-598 (1990)
3. K.Lear, K.Yoh, J.S.Harris Jr, "Monolithic Integration of GaAs/AlGaAs Resonant Tunnel Diode Load and GaAs Enhancement MESFET Drivers for Tunnel Diode FET Gate Logic," Inst. Phys. Conf. Ser., 106, pp593-598 (1989)
4. Kanji Yoh, J. S. Harris Jr.,"Complementary MODFET Circuits Consisting of Pseudomorphic NMODFET and Double Heterojunction PMODFET by Selective Molecular Beam Epitaxy," Presented at International Electron Device Meeting, (Washington D.C., U.S.A) (1987) Published in the Technical Digest of IEEE International Electron Devices Meeting (IEDM), pp892-894 (1987)
＜Related Project
　- Joint project（Hitachi Ltd.）
＜Related Research（Other groups）
　- Non-linear phenomena（Hokkaido University, Profesor Akera�s Lab,）
　- Non-linear Phenomena and ReactionDiffusion SystemsApplied to Electronic Circuits
（Hokkaido University, Professor Amemiya�s Lab）
　- Research groups working on non-equilibrium systems

To the top of the page

　　―Molecular Beam Epitaxy―
　　― Quantum Dots, Quantum Wires―
　　― Fabrication and Characterization of Quantum Nanostructures―

We investigate the fabrication technology of quantum nanostructures such as quantum dots, quantum wires, and hybrid structures with dissimilar materials using combined technology of nano lithography and Molecular Beam Epitaxy (MBE). A hybrid structure includes heteroepitaxy of ferromagnetic metals on semiconductors. The quantum nanostructures are sought to fabricate a new type of device to deal with quantum information processing
Fig.3 shows an example of arrayed InAs quantum dots on patterned substrate and Fig.4 shows an example of quantum wire by selective-doping mechanism.

＜Related Papers (Published)
1. Y.Katano, T.Doi, H.Ohno, and K.Yoh, "Surface potential analysis on doping superlattice by electrostatic force microscope," Appl.Surf.Sci., 188 (2002) pp.399-402
2. Kanji Yoh and Shingo Takabayashi, "Fabrication of GaAs quantum wires by natural selsective selective doping and its characterization by electrostatic force microscope," J.Vac.Sci.Technol.B 18 (3), pp.1675-1679 (2000)
3. Kanji Yoh, Toshiya Saitoh, Arata Tanimura and Ryuusuke Nakasaki,"Self-assembled InAs dots and quantum wires fabricated on patterned (311)A GaAs substrates by molecular beam epitaxy," J. Electronic Materials, vol.28,No.5, pp.457-465 (1999).
4. S.Takabayashi, H.Kazama, Y.Kitasho and K. Yoh, "Structural and transport characterization of AlGaAs/GaAs quantum wires formed by selective doping mechanism," Inst. Phys. Conf. Ser. No.162, pp.391-396 (1999).
5. Kanji Yoh and Sanshiro Shiina, "Crossover from Coulomb blockade to single electron memory mode in a d-dopedchannel GaAs split-gate transistor embedded with InAs dots in adjacent to the channel," The Physics of Semiconductors (World Scientific 1999).
6. Kanji Yoh, Ryuusuke Nakasaki and Shingo Takabayashi, " Self-assembled InAs dots and quantum wires fabricated on patterned (311)A GaAs substrates by molecular beam epitaxy," J.Crystal Growth 201/202, pp.1164-1167 (1999).

To the top of the page