Development of device emitting pure circularly polarized light by injecting spin-polarized electrons and elucidation of its emission mechanism

2018 Fiscal Year Final Research Report

• Project/Area Number: 17K14104
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Applied materials
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Nozomi Nishizawa 東京工業大学, 科学技術創成研究院, 助教 (80511261)
• Research Collaborator: Munekata Hiro
• Project Period (FY): 2017-04-01 – 2019-03-31
• Keywords: スピントロニクス / スピンフォトニクス / 円偏光 / 発光ダイオード / 酸化絶縁膜 / スピン注入

Outline of Final Research Achievements

Aiming at stable emission of pure circularly polarized light (CPL) from spin-polarized emitting diodes (Spin-LEDs) and elucidation of its emission mechanism, we have studied the formation of high-quality tunneling barrier layer for spin injection from magnetic electrodes into semiconductors. First, we improve the crystallinity of an ultra-thin oxide tunnel barrier and the interface state between oxide and semiconductor layers by optimizing the growth condition. However, the yields of pure CPL emission has not been improved. Next, hybrid tunneling barrier (HTB) which is inserted AlAs layer between a crystalline aluminum oxide layer and semiconductor-based LED structure has been adopted, enhancing the reproducibility drastically. Stable pure CPL emission from spin-LED with HTB enable us to consider CPL emission spectra systematically. As results, the hypothesis based on the asymmetric spin-relaxation and asymmetric re-abroption has been proposed as a possible mechanism.

Free Research Field

スピントロニクス

Academic Significance and Societal Importance of the Research Achievements

Spin-LEDはこれまでの研究により電気的に偏光制御が可能で、外部磁場なしに純粋円偏光を発光する実用的な円偏光光源となり得ると示されてきたが、素子の安定性に問題があった。本研究の成果であるHBTにより安定的な円偏光発光が得られるようになり実用に大きく前進したと言え、半導体スピントロニクス最初の室温動作する実用デバイスになると期待される。また、学術的にも円偏光増強のメカニズムの解明が進み、円偏光が伝搬する半導体中におけるキャリアと光の非線形効果という新たな研究課題を創出したと考えられる。