Intervalley splitting and intersubband transitions in n-type Si/SiGe quantum wells: pseudopotential vs. effective mass calculation

Abstract

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.

7 pages, 8 figures

References in corpus (6)

• Valley Splitting Theory of SiGe/Si/SiGe Quantum Wells
• Valley splitting in strained silicon quantum wells
• Spin and valley-orbit splittings in SiGe/Si heterostructures
• The Two-flux Composite Fermion Series of Fractional Quantum Hall States in Strained Si
• Strong enhancement of the valley splitting in a 2D electron system in silicon
• Simulation of Si:P spin-based quantum computer architecture

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• Intersubband carrier scattering in n- and p-Si/SiGe quantum wells with diffuse interfaces
• Theory and design of quantum cascade lasers in (111) n-type Si/SiGe
• Origin of giant valley splitting in silicon quantum wells induced by superlattice barriers
• Well-width dependence of valley splitting in Si/SiGe quantum wells
• Theoretical Prediction of Enhanced Thermopower in n-doped Si/Ge Superlattices using Effective Mass Approximation
• Fragility of the Dirac Cone Splitting in Topological Crystalline Insulator Heterostructures