Structural and optical properties of Al_1-xIn_xN epilayers on GaN template grown by metalorganic chemical vapor deposition

This paper reports that Al_1-xIn_xN epilayers were grown on GaN template by metalorganic chemical vapor deposition with an In content of 7%--20%. X-ray diffraction results indicate that all these Al_1-xIn_xN epilayers have a relatively low density of threading dislocations. Rutherford backscattering/channeling measurements provide the exact compositional information and show that a gradual variation in composition of the Al_1-xIn_xN epilayer happens along the growth direction. The experimental results of optical reflection clearly show the bandgap energies of Al_1-xIn_xN epilayers. A bowing parameter of 6.5 eV is obtained from the compositional dependence of the energy gap. The cathodoluminescence peak energy of the Al_1-xIn_xN epilayer is much lower than its bandgap, indicating a relatively large Stokes shift in the Al_1-xIn_xN sample.