Research on a single electron transistor with self-assembled quantum dots and its prototype fabrication

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We have proposed a heterostructure transistor embedded with InAs quantum dots which could manipulate electron states (including spin states) in the dot. The heterostructure FET with quantum dots buried in adjacent to the channel, was shown to have apotential of quantum bit ("qubit") when the spin of channel electrons are selectable by spin injection method. Realization of this idea depends on the success of Rashba effect control and spin injection. The feasibility of these important toipcs has been investiagted and summarized below.Large spin-orbit coupling in InAs quantum well structure which was grown on InAs substrate by analyzing Shubnikov-de Haas oscillation. The obtained spin-orbit interaction coefficient was 【approximately equal】 30x10^<-12>eVm. The number was found to be much greater than that of GaAs or InGaAs on InP and almost comparable to the previous experimets where measured InAs heterostructures were associated with possible effects from interface states or possible residual strain or possible interplay of several sublevelsl.The "spin-injection" from ferromagnetic film into semiconductors has been investigated. The crystal Fe growth on InAs by molecular beam epitaxy at low temperature of 23℃ was found to yield better spin injection characteristics. The electroluminescence of spin polarized electrons injected from ferromagnets into InAs therough Fe/InAs junction was measured, and verified spin injection with polarization of 【approximately equal】20%.