Fabrication of Quantum Wires Based on Selective Doping Mechanism and Its Application to Functional Devices Using Quantum Parallelism

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We have aimed at establishing our original fabrication methods of quantum wires and further developing the method to apply to the realization of the "quantum devices". We have investigated the fabrication and the electronic characterization of the quantum wires grown on facets on (311)A GaAs substrates in addition to the (100) GaAs substrates. Cryogenic temperature measurement on quantum wire transistors showed clear quantum wire characteristics. The major results are described below. (I) We have established a new fabrication methods of device quality quantum wires based on selective doping mechanism on patterned sustrates. Unlike the advanced nano-lithography technique such as electron beam lithography or scanning probe method, the present method was demonstrated to be able to process wafer scale fine structures in one step of growth. The obtained quantum wires were shown to maintain high quality along mm long structurally by Electrostatic Force Microscopy. (ii) Single electron oscill … More tion was observed near pinch-off conditions at 2K. Detailed measurements changing temperature and the external magnetic fields relealed that the potential ondulation along the quantum wire resulted in series of isolated potential pockets of 6meV or so deep. Present results shows degree of flatness of the confinement potential along the mm long quantum wires based on the present method. In addition, we have observed clear conductance oscillations which are clear evidence of 1-dimensional conduction at 77K and 4K. This result strongly indicates that one-dimensional conduction is achieved at up to 77K or more without mode mixing. (iii) Transistor characteristics of the "single wire" transistor were also investigated. The I .5μm gate transistor showed the transconductance of 580mS/mm and 650mS/mm at 300K and 77K respectively. These results belong to high end of the modulation doped transistors based on GaAs/AlGaAs. This result indicates successful fabrication of high quality one-dimensional electron systems. It also revealed extremely small gate leakage current of the order of tens of picoamperes. Together with this low leakage characteristics, the present quantum wire approach was shown to have high potentail of integrated quantum qire transistor circuits based on classical and quantum funcional principles. Less