n型Si/SiGe量子阱的谷间分裂和子带间跃迁：赝势与有效质量的关系
Intervalley splitting and intersubband transitions in n-type Si/SiGe quantum wells: pseudopotential vs. effective mass calculation
摘要：
低维Si/SiGe异质结构中导带态之间的谷间混合引起名义上简并能级之间的分裂。采用对称双谷有效质量近似和经验赝势方法计算了不同类型量子阱中的电子态。这两种方法之间的一个相当好的协议被发现，前者是更快的计算。分裂除了是阱宽的振荡函数外，几乎与面内波矢无关，是界面梯度大小的增函数。虽然该模型是定义为对称的包络电位，它被证明是保持合理的准确性略有不对称的结构，如双量子阱，使它可以接受的多层子带间光学器件的模拟。在这两种近似下研究了子带间的光学跃迁，结果表明，在大多数情况下，谷分裂会导致线宽加宽，尽管在极端条件下可能会产生跃迁线双峰。
英文摘要：
Intervalley mixing between conduction-band states in low-dimensional Si/SiGe heterostructures induces splitting between nominally degenerate energy levels. The symmetric double-valley effective mass approximation and the empirical pseudopotential method are used to find the electronic states in different types of quantum wells. A reasonably good agreement between the two methods is found, with the former being much faster computationally. Aside from being an oscillatory function of well width, the splitting is found to be almost independent of in-plane wave vector, and an increasing function of the magnitude of interface gradient. While the model is defined for symmetric envelope potentials, it is shown to remain reasonably accurate for slightly asymmetric structures such as a double quantum well, making it acceptable for simulation of multilayer intersubband optical devices. Intersubband optical transitions are investigated under both approximations and it is shown that in most cases valley splitting causes linewidth broadening, although under extreme conditions, transition line doublets may result.
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