Refractive indices of wurtzite and zincblende GaN

Refractive index measurements on both wurtzite and zincblende GaN films grown by plasma-enhanced molecular beam epitaxy are reported. For birefringent uniaxial wurtzite GaN samples the index of refraction was measured along the crystalline axis. In this direction the index is 2.78 at 3.4 eV. For cubic GaN films grown on GaAs substrates, the refractive index is 2.91 at 3.2 eV. Estimation of the confinement factor for optimised waveguides based a combination of III-V nitrides indicates very favourable values for laser operation.