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Theory
Temperature effects
Thermal expansion of the material is described through the change of lattice constant:
where aT is a linear expansion coefficient. Nonequal changes of the layers lattice constant in a heterostructure change the internal strain due to the lattice mismatch and lead to the modification of the band structure.
The temperature dependence of the bandgap is taken into account according to the empirical Varshni expression [6]
where α and β are adjustable parameters, Eg(0) is band gap at zero temperature. This expression describes a decrease of band gap when the temperature increases.
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