Dielectric function and refractive index of GaBi x As 1‐ x ( x = 0.035, 0.052, 0.075)

MBE grown GaBiAs epitaxial layers with Bi content of 3.5%, 5.2%, and 7.5%, sandwiched between GaAs, have been investigated by spectroscopic ellipsometry in the infrared and absorption threshold spectral regions. The real and imaginary parts of the dielectric function of GaBiAs indicate bandgap E g and spin‐orbit splitting Δ 0 + values close to literature data. The refractive index of GaBiAs in the IR region 0.2–0.8 eV exceeds that of GaAs by ca. 0.8%, 2.3%, and 3.6%, for Bi content 3.5 %, 5.2%, and 7.5%, respectively (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)