The temperature dependence of the 1s exciton energy has been measured in Zn1—xMgxSe epitaxial films at compositions x = 0, 0.07, 0.12, and 0.19 from 2 K up to 280 K. Detailed numerical fits of the individual temperature dependences are provided on the basis of an analytical four-parameter representation developed recently by one of the authors. These are compared with previously used three-parameter models of Viña et al. and Varshni. The x-dependence of the exciton energy, E1s(T, x), and of the fundamental band gap energy, Eg(T, x), is given to very good approximation by linear functions of the composition x for any T from absolute zero up to room temperature. A comparison with recent room temperature band gap energy data by Jobst et al. shows that this linear dependence holds up to x ≈︂ 0.7. The magnitudes of the model-dependent empirical parameters, which control the temperature dependence of the band gap energy in different compounds, are found to change significantly with increasing magnesium content. From the magnitude of the effective phonon temperature, particularly in the case of ZnSe, we conclude that the main contributions to the band gap shrinkage effect are due to acoustic phonons.
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P�ssler et al. (1997) studied this question.