Structural and optical properties of MOCVD InAlN epilayers

We have studied the structural and optical properties of InAlN alloys with compositions nearly lattice-matched to GaN. Scanning electron microscopy measurements reveals a good overall surface quality, with some defect structures distributed across the surface whose density increases with the InN concentration. On the other hand, Raman scattering experiments show three peaks in the frequency range between 500 and 900 cm−1, which have been assigned to InN-like and AlN-like E2 modes and A1(LO) mode of the InAlN. These results agree with theoretical calculations previously reported where two-mode and one-mode behavior was predicted for the E and A(LO) modes, respectively. Photoluminescence and photoluminescence excitation allowed us to determine the emission and absorption energies of the InAlN epilayers. Both energies display a redshift as the InN fraction increases. We find a roughly linear increase of the Stokes shift with InN fraction, with Stokes shift values of ≈0.5 eV in the composition range close to the lattice-matched condition.