Impurity Effects on Photoluminescence in Lateral Epitaxially Overgrown GaN

Using a two-photon laser scanning microscope, the spectral and intensity variations of photoluminescence (PL) in a lateral epitaxial overgrown GaN film were mapped with submicron resolution. The PL results are correlated with carrier density variation obtained by confocal Raman microscopy and surface Fermi level positions obtained by scanning Kelvin force microscopy. 

Near bandgap emission spectra taken in the wing regions provide support for the previously proposed compensated impurity band, which arises from incorporation of a high concentration of impurities resulting in a carrier density of ~ 1020 cm-3.