Enhancement and field-effect control of terahertz gain in semiconductor superlattices

• Project/Area Number: 25707026
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Partial Multi-year Fund
• Research Field: Condensed matter physics I
• Research Institution: Nagaoka University of Technology (2014-2016); Nagoya University (2013)
• Principal Investigator: Unuma Takeya 長岡技術科学大学, 工学(系)研究科(研究院), 准教授 (20456693)
• Project Period (FY): 2013-04-01 – 2017-03-31
• Project Status: Completed (Fiscal Year 2016)
• Budget Amount: ¥28,990,000 (Direct Cost: ¥22,300,000、Indirect Cost: ¥6,690,000); Fiscal Year 2016: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000); Fiscal Year 2015: ¥2,340,000 (Direct Cost: ¥1,800,000、Indirect Cost: ¥540,000); Fiscal Year 2014: ¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000); Fiscal Year 2013: ¥20,280,000 (Direct Cost: ¥15,600,000、Indirect Cost: ¥4,680,000)
• Keywords: 半導体超格子 / テラヘルツ / 光学利得 / シュタルク効果 / 量子ビート / 非平衡系 / 半導体物性 / 超格子 / テラヘルツ/赤外材料・素子

Outline of Final Research Achievements

We investigated the amplification effect on (i.e., the gain for) terahertz electromagnetic waves in semiconductor superlattices with an emphasis on its physical nature and controllability at high temperatures, which artificial crystals contained an alternate stack of nanometer-thick GaAs and AlAs layers. Electrons created by optical pulses under dc voltage in the stacking direction were found to exhibit temporal waveforms of terahertz emission with a voltage- controlled oscillation frequency and a unique initial phase throughout the temperature range of 80-298 K. The complex conductivity spectra obtained using the phase information have offered direct evidence for the existence of room-temperature terahertz gain in semiconductor superlattices that originates from a capacitive nature of the electron system (without the conventional concept of population inversion).

Research Products

• [Journal Article] Capacitive response and room-temperature terahertz gain of a Wannier-Stark ladder system in GaAs-based superlattices (2016)
  • Author(s): Akiyoshi Naka, Kazuhiko Hirakawa, Takeya Unuma
  • Journal Title: Applied Physics Express Volume: 9 Issue: 11 Pages: 112101-112101
  • DOI: 10.7567/apex.9.112101
  • NAID: 210000138090
  • Peer Reviewed / Open Access / Acknowledgement Compliant
• [Presentation] GaAs系超格子におけるテラヘルツ複素伝導度スペクトルの温度依存性II (2017)
  • Author(s): 中 章圭，平川 一彦，鵜沼 毅也
  • Organizer: 日本物理学会第72回年次大会
  • Place of Presentation: 大阪大学豊中キャンパス(大阪府豊中市）
• [Presentation] GaAs系超格子におけるテラヘルツ複素伝導度スペクトルの温度依存性 (2016)
  • Author(s): 中 章圭，鵜沼 毅也
  • Organizer: 日本物理学会第71回年次大会
  • Place of Presentation: 東北学院大学泉キャンパス（宮城県仙台市）
  • Year and Date: 2016-03-21