Ellipsometric study of the temperature dependences of the dielectric function and the critical points of AlSb at temperatures from 300 to 803 K
We report the complex pseudodielectric function < ∊ > = < ∊ 1 > + i < ∊ 2 > of an oxide-free AlSb film for energies from 0.7 to 5.0 eV and temperatures from 300 to 803 K. The 1.5- μm-thick film was grown on a (001) GaAs substrate by using molecular beam epitaxy. We maintained the film in an ultrahigh vacuum to prevent oxidation artifacts and used a rotating-compensator ellipsometer to obtain the optical properties. Critical-point (CP) energies were obtained by numerically calculating second energy derivatives of the data. Blue shifts of the CP energies and sharper structures were observed with decreasing temperature. The calculated CP energies were fit to a linear equation.