Impact of near-surface defects and morphology on ZnO luminescence

Abstract

We have used depth-resolved cathodoluminescence spectroscopy (DRCLS) to measure the distribution of deep level defects at and below the surface of ZnO crystals grown by vapor phase transport, hydrothermal, and melt-growth methods. DRCLS reveals large variations in defect distributions with depth on a nanometer scale that correlate with maps of potential and surface morphology measured by Kelvin probe force and atomic force (AFM) microscopies, respectively. A strong correlation between the optical emission efficiency of the nanoscale subsurface region and the AFM surface roughness reveals a figure of merit for substrate polishing and etching.