Microcomposition and luminescence of InGaN emitters

Using wavelength dispersive X-ray (WDX) spectrometers on an electron probe micro-analyser (EPMA) the indium content of a number of homogeneous and inhomogeneous InGaN epitaxial layers has been accurately mapped. The addition of a spectrometer and silicon CCD array to the light microscope, which shares the same focus as the electron microscope, enables cathodoluminescence spectra to be collected from exactly the same spot as sampled by the WDX spectrometers. As a result the dependencies of the luminescence energy and linewidth on the local indium nitride fraction can be investigated with greater confidence than in earlier reports, where separate measurements of luminescence and composition were required. Samples studied have indium nitride fractions ranging from