A systematic study of the quasi-Fermi level pinning in various interband cascade lasers (ICLs) is reported. These ICLs, with either type-II or type-I quantum well active regions, cover the mid-infrared wavelength range from 3 to $6~\mu \text{m}$ and can operate in continuous wave (cw) at room temperatures and above. It was found that the quasi-Fermi level can be pinned in many ICLs over a wide range of temperature, which is associated with an observed drop of differential resistance at threshold. For the first time, the quasi-Fermi level pinning was demonstrated in ICLs at room temperature. The temperature dependence of the quasi-Fermi level pinning in ICLs was also examined. A pinning factor is introduced to evaluate how well the quasi-Fermi level is pinned in ICLs with different configurations and lasing wavelengths. Also, it was found that the quasi-Fermi level pinning disappeared in some ICLs where an obvious drop of differential resistance could not be observed at the threshold. Furthermore, the quasi-Fermi level pinning was found to be correlated to the doping concentration in electron injectors in ICLs. Possible mechanisms and implications related to the quasi-Fermi level pinning are discussed.

中文翻译：

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带间级联激光器中的准费米能级钉扎

报告了对各种带间级联激光器 (ICL) 中准费米能级钉扎的系统研究。这些具有 II 型或 I 型量子阱有源区的 ICL 覆盖了 3 到 $6~\mu \text{m}$ 的中红外波长范围，并且可以在室温和连续波 (cw) 中工作以上。发现准费米能级可以在很宽的温度范围内固定在许多 ICL 中，这与在阈值处观察到的差分电阻下降有关。首次在室温下在 ICL 中证明了准费米能级钉扎。还检查了 ICL 中准费米能级钉扎的温度依赖性。引入了钉扎因子来评估准费米能级在具有不同配置和激光波长的 ICL 中的钉扎效果。还，发现准费米能级钉扎在一些 ICL 中消失，在阈值处无法观察到明显的微分电阻下降。此外，发现准费米能级钉扎与 ICL 中电子注入器的掺杂浓度相关。讨论了与准费米能级钉扎相关的可能机制和影响。