Nonlinear transport in quantum-cascade lasers: The role of electric-field domain formation for the laser characteristics
Nonlinear transport in quantum-cascade lasers: The role of electric-field domain formation for the laser characteristics
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DOI：
10.1063/1.3573504
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发表时间：
2011-04
影响因子：
3.2
通讯作者：
M. Wienold;L. Schrottke;M. Giehler;R. Hey;H. Grahn
中科院分区：
文献类型：
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作者：
M. Wienold;L. Schrottke;M. Giehler;R. Hey;H. Grahn
半导体超晶格中的许多非线性输运现象与负微分电阻（NDR）的出现和电场域（EFD）的形成有关。经过深入研究的常见现象包括电流-电压 (I-V) 特性的不连续性和电流自振荡。 1-3 尽管量子级联激光器 (QCL) 基于更加复杂的异质结构，但已知存在类似的效应。在中红外量子级联结构 4 以及为太赫兹发射设计的量子级联结构中观察到 EFD 低于阈值。 5 在这项工作中，我们报告了太赫兹 QCL，其中 EFD 的存在会影响连续波 (cw) I-V 和高于阈值的输出功率特性，从而导致在实验激光特性中观察到异常的不连续性。我们进一步提出了一种在存在 NDR 和 EFD 的情况下模拟 QCL 特性的方法。 QCL 模拟通常是在每个周期内电压降相等的假设下进行的，这意味着每个周期内都是电荷中性。 6-8 这种被标记为周期性电压降 (PVD) 的条件具有大大降低数值复杂性的优点，但排除了 EFD 的形成，EFD 需要跨多个周期的电荷积累和耗尽。我们将展示如何使用描述弱耦合超晶格中非线性输运的方程来模拟存在 EFD 的情况下 QCL 的输运和输出功率特性。
Many nonlinear transport phenomena in semiconductor superlattices are related to the occurrence of negative differential resistance (NDR) and the formation of electric-field domains (EFDs). Common phenomena, which have been intensively investigated, include discontinuities in the current-voltage (I-V) characteristics and current self oscillations. 1‐3 Although quantum-cascade lasers (QCLs) are based on significantly more complex heterostructures, similar effects are known to exist. EFDs have been observed below threshold in mid-infrared quantum-cascade structures 4 and also in quantum-cascade structures designed for THz emission. 5 In this work, we report on terahertz QCLs, for which the presence of EFDs affects the continuous wave (cw) I-V and output power characteristics above threshold, resulting in the observation of unusual discontinuities in the experimental laser characteristics. We further propose a method to simulate the QCL characteristics in the presence of NDR and EFDs. QCL simulations are usually performed under the assumption of an equal voltage drop in each period, which implies charge neutrality in each period. 6‐8 Such conditions, labeled periodic voltage drop (PVD), have the advantage of a much reduced numerical complexity, but exclude the formation of EFDs, which requires charge accumulation and depletion across multiple periods. We will show how the equations describing the nonlinear transport in weakly coupled superlattices can be used to simulate the transport and output power characteristics of QCLs in the presence of EFDs.