Temperature dependence analysis of the thermo-optic effect in silicon by single and double oscillator models

The thermo-optic coefficient (dn/dT) of crystalline silicon has been critic ally analyzed in the temperature range 300-600 K, at the fiber optic commun ication wavelength of 1.5 mum. The temperature dependence has been attribut ed to the variation of the interband transition energies at some critical p oints of the silicon band structure. The experimental data have been fitted using single and double oscillator models. In particular, the double oscil lator model, which is physically correlated to the silicon band structure, has been exploited to extrapolate the temperature dependence of the interba nd transition energies at some points (critical points) of the combined den sity of states. The extracted parameters are in good agreement with the dat a reported in the literature. Finally, in connection with both of the oscil lator approximations, an analysis based on thermodynamic considerations is carried out, and electron-hole formation entropy and specific heat are calc ulated. The consistency of the obtained results validate the reliability of the proposed analysis. (C) 2000 American Institute of Physics. [S0021- 897 9(00)07101-8].