MEASUREMENT OF GAAS TEMPERATURE-DEPENDENT OPTICAL-CONSTANTS BY SPECTROSCOPIC ELLIPSOMETRY

Temperature-dependent optical constants (30-degrees-C<T<650-degrees-C) of semi-insulating GaAs in the range of 1.24-5.00 eV were measured us ing spectroscopic ellipsometry (SE) inside a specially designed molecu lar beam epitaxy chamber. Because of the lack of native oxides and sur face adsorbates, a simple two-phase model (vacuum/substrate) could be used to calculate optical constants from the ellipsometry data. A Lore ntz oscillator model with seven oscillators was used to fit the epsilo n1 and epsilon2 experimental data to determine the temperature-depende nt interband transition energies, E1 and E1 + DELTA1. Changes in the d ielectric function at different surface temperatures would allow SE to be used as a tool to accurately measure the surface temperature of Ga As. Accurate knowledge of the temperature-dependent optical constants is also useful for the design of optical devices.