Measurement of GaAs temperature-dependent optical constants by spectroscopic ellipsometry

Temperature-dependent optical constants (30 °C<T<650 °C) of semi-insulating GaAs in the range of 1.24–5.00 eV were measured using spectroscopic ellipsometry (SE) inside a specially designed molecular beam epitaxy chamber. Because of the lack of native oxides and surface adsorbates, a simple two-phase model (vacuum/substrate) could be used to calculate optical constants from the ellipsometry data. A Lorentz oscillator model with seven oscillators was used to fit the ε1 and ε2 experimental data to determine the temperature-dependent interband transition energies, E1 and E1+Δ1. Changes in the dielectric function at different surface temperatures would allow SE to be used as a tool to accurately measure the surface temperature of GaAs. Accurate knowledge of the temperature-dependent optical constants is also useful for the design of optical devices.