Electric field control of spin polarity in spin injection into InGaAs quantum dots (QDs) from a tunnel-coupled quantum well (QW) was studied. The degree of freedom of the spin state in high-density QDs will play an important role in semiconductor spintronics such as a spin-functional optical device, where it is crucial to establish spin injection and manipulation by electric fields. To solve this subject in a layered device structure, electric field effects on spin injection from a 2-dimensional QW into 0-dimensional QDs were studied. Spin-polarized electrons were photo-excited in a QW and then injected into QDs via spin-conserving tunneling. After the injection, parallel spin states to the initial spin direction in the spin reservoir of QW were observed in QDs as a result of efficient spin injection, by circularly polarized photoluminescence indicating spin states in the QDs. Moreover, reversal of spin polarity was clearly observed at QD ground states, depending on the electric fields applied along the QD-QW growth direction. The tunneling rate of an electron is different from that of a hole and largely depends on the electric field, owing to electric field induced modifications of the coupled QD-QW potential. This results in negative trions in the QDs with anti-parallel spins to the initial ones in the QW, which is evidently supported by a significant effect of p-doping. The polarization degrees of both spin polarities can be optimized by excitation-spin density, in addition to the electric field strength.
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1 April 2019
Research Article|
April 01 2019
Electric field control of spin polarity in spin injection into InGaAs quantum dots from a tunnel-coupled quantum well
Hang Chen
;
Hang Chen
Graduate School of Information Science and Technology, Hokkaido University
, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan
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Satoshi Hiura
;
Satoshi Hiura
Graduate School of Information Science and Technology, Hokkaido University
, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan
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Junichi Takayama
;
Junichi Takayama
Graduate School of Information Science and Technology, Hokkaido University
, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan
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Soyoung Park;
Soyoung Park
Graduate School of Information Science and Technology, Hokkaido University
, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan
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Kazuhisa Sueoka;
Kazuhisa Sueoka
Graduate School of Information Science and Technology, Hokkaido University
, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan
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Akihiro Murayama
Akihiro Murayama
a)
Graduate School of Information Science and Technology, Hokkaido University
, Kita 14, Nishi 9, Kita-ku, Sapporo 060-0814, Japan
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a)
E-mail: murayama@ist.hokudai.ac.jp
Appl. Phys. Lett. 114, 133101 (2019)
Article history
Received:
January 27 2019
Accepted:
March 15 2019
Citation
Hang Chen, Satoshi Hiura, Junichi Takayama, Soyoung Park, Kazuhisa Sueoka, Akihiro Murayama; Electric field control of spin polarity in spin injection into InGaAs quantum dots from a tunnel-coupled quantum well. Appl. Phys. Lett. 1 April 2019; 114 (13): 133101. https://doi.org/10.1063/1.5090419
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