Scanning cathodoluminescence as a probe of surface recombination in phosphors excited at low electron energies

Abstract

Scanning cathodoluminescence (SCL) is a technique that has been widely used to categorize local minority carrier lifetime nonuniformities in bulk and thin film semiconductors. In the case of phosphor powders it has been less popular, partly because the collection and scattering of light generated in an array of particles complicates the extraction of quantitative information about light generation efficiency. Here we demonstrate that by coupling SCL with modern digital imaging manipulation techniques, we can extract quantitative information about the beam energy dependence of phosphor cathodoluminescence with high spatial resolution. A number of common phosphors are examined and a wide range of behavior is observed. We find that materials like ZnS:Ag and SrGa2S4:Eu display uniformly high nonradiative surface energy losses, while other materials like ZnO:Zn have surface losses which are spatially very nonuniform.