Doping-Induced Contrast in the Refractive Index for GaInN/GaN Structures at Telecommunication Wavelengths

The authors report on the doping-induced contrast in the refractive index in GaInN/GaN-structures at telecommunication wavelengths. This contrast appears because of the plasma edge effect which has been directly observed in reflectance spectrum of GaInN:Si-layer. The refractive index has been calculated from the reflectance by using Kramers–Kronig relations and measured by ellipsometry. It has been found that the contrast between the refractive index of GaInN:Si and GaN layers equals ~15% at the wavelength of 1.55-µm and the absorption coefficient is still close to zero at this wavelength. It means that GaN-based waveguides operating at 1.55-µm can be obtained by Si-doping.