Wang Li, Lin Tsung-Tse, Chen Mingxi, Wang Ke, Hirayama Hideki
THz Quantum Device Team, RIKEN Center for Advanced Photonics, 519-1399 Aramaki-aza Aoba, Aoba-ku, Sendai, 980-0845, Japan.
School of Electronics Science and Engineering, Nanjing University, 163 Xianlin Street, Qixia District, Nanjing, 210046, China.
Sci Rep. 2021 Dec 8;11(1):23634. doi: 10.1038/s41598-021-02301-3.
The key challenge for terahertz quantum cascade lasers (THz-QCLs) is to make it operating at room-temperature. The suppression of thermally activated leakages via high lying quantum levels is emphasized recently. In this study, we employ the advanced self-consistent method of non-equilibrium Green's function, aiming to reveal those kinds of leakages in the commonly used THz-QCL designs based on 2-, 3- and 4-quantum well. At the high temperature of 300 K, if all the confined high lying quantum levels and also the continuums are included within three neighboring periods, leakages indeed possess high fraction of the total current (21%, 30%, 50% for 2-, 3- and 4-quantum well designs, respectively). Ministep concept is introduced to weaken those leakage channels by isolating the desired levels from high lying ones, thus the leakages are well suppressed, with corresponding fractions less than 5% for all three designs.
太赫兹量子级联激光器（THz-QCLs）面临的关键挑战是使其能够在室温下工作。最近，通过高能级量子态抑制热激活泄漏受到了重视。在本研究中，我们采用先进的非平衡格林函数自洽方法，旨在揭示基于2、3和4量子阱的常用THz-QCL设计中的此类泄漏情况。在300 K的高温下，如果在三个相邻周期内包含所有受限的高能级量子态以及连续态，则泄漏电流在总电流中所占比例确实很高（对于2、3和4量子阱设计，分别为21%、30%和50%）。引入微步概念，通过将所需能级与高能级隔离开来削弱这些泄漏通道，从而有效抑制了泄漏，所有三种设计的相应比例均小于5%。
