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

2016 Fiscal Year Final Research Report

• 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
• 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

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).

Free Research Field

半導体物性