Dielectric function of AlInN nearly lattice-matched to GaN

Al1-xInxN material with ∝18 % indium content is lattice matched to GaN and has lot of potential applications for photonic and electronic devices. In our work we carry out a comprehensive study of high-quality MOCVD-grown c-plane Al1-xInxN films with In content ranging from 14 to 22 %. High resolution X-ray diffraction measurements revealed that AlInN films are pseudomorphically grown to GaN. Ellipsometry studies were conducted on the AlInN samples in the photon energy range from 1 to 10 eV. For the first time, complex effective ordinary dielectric function (DF) of AlInN nearly lattice-matched (LM) to GaN was extracted and the critical points of the band structure were determined. The pronounced optical transitions in the high-photon energy part of the DF indicate already promising optical quality of the AlInN films. The sharp onset of the imaginary part of the DF defines the direct absorption edge which is red-shifted for the AlInN samples with higher In content. High frequency dielectric constants were estimated from the real part of the DF in the transparent region. The band gap values are evaluated including the influence of strain.