Temperature-dependent dielectric functions of InP between 25 K and 700 K

We report the dielectric functions of InP at temperatures between 25 K and 700 K measured by using spectroscopic ellipsometry (SE) in the energy range from 1.19 to 6.57 eV. A blue shift and a separation of critical point (CP) structures were observed at low temperatures, which is explained by the reduced electron-phonon interaction and by the thermal expansion. The values of the CP energies were determined from numerically-calculated second energy derivatives of the data. Separation of the E₂ CP structures (4 - 6.5 eV), which could not be detected at room temperature, was clearly shown at low temperatures. We report the temperature dependences of the E₂' and the E₁' CP energies, which have not been observed so far by using SE.