A scanning near-field optical microscope was used to obtain local photoluminescence and electroluminescence spectra, from GaN/GaInN/AlGaN LED structures, with a lateral resolution of better than 200nm. The optical information was compared with defect positions made visible to atomic force microscopy by wet chemical etching. Peak wavelength maps obtained from the scanning near-field optical microscopy data revealed spatial regions, with various emission wavelengths, having typical dimensions of 200 to 500nm; associated with the defect structure. No evidence was found for small-scale fluctuations of emission wavelength as expected in the case of phase separation of InGaN.

Correlation of Defects and Local Bandgap Variations in GaInN/GaN/AlGaN LEDs. F.Hitzel, A.Hangleiter, S.Bader, H.J.Lugauer, V.Härle: Physica Status Solidi B, 2001, 228[2], 407-10