Temperature dependence of optical transitions between electronic energy levels in semiconductors

We propose a model to describe temperature-dependent electronic transitions using an effective electron-ion interaction. We present a nonperturbative calculation of the temperature dependence of the forbidden energy gap of CdTe crystals. The results are compared with similar calculations using the statistical-function method and both give good agreement with experimental data. It is also demonstrated that the thermal expansion of the lattice plays a minor role for the temperature variation of the electronic energy levels.