Optical functions of bulk and epitaxial GaSb from 0.0025 to 6 eV

The complex refraction index and dielectric functions of GaSb bulk (both p and n-type) and MBE film were accurately determined from 0.0025 to 6 eV by using reflectance and ellipsometric spectroscopies. These functions, which satisfy the Kramers-Kronig causality relations, appear independent on the doping (≤2×1017cm−3) in the interband transition region. In particular, in comparison with previous data from literature, the E0 fundamental gap is well evidenced for all the samples. Moreover, the optical functions around the gap are very different from those previously reported and the refractive index was modeled by a Sellmeier dispersion relation. The free-carriers instead strongly influence the far-infrared restrahlen region due to the phonon-plasmon coupling. In this range the optical functions were well fitted by Drude-Lorentz oscillators.