Lawrence Berkeley National Laboratory

Transmission Electron Microscopy (TEM) and optical measurements obtained from InN and In1-xGaxNfilms (0 < x < 0.54) grown by Molecular Beam Epitaxy are presented. Energy gaps measured byabsorption, PR, and PL for InN films grown on c-plane Al2O3 were in the range of 0.7 eV. No In or otherinclusions were observed in these films, ruling out the possibility of a strong Mie scattering mechanism. Inthe In1-xGaxN films the relationship between the structural properties and the optical properties, inparticular the presence or absence of a Stokes shift between absorption and PL, is discussed. TEM studiesshow that high quality layers do not have a Stokes shift. Some films had compositional ordering; thesefilms also showed a shift between absorption edge and luminescence peak.