A method of normalizing cathodoluminescence images of electron transparent foils for thickness contrast applied to InGaN quantum wells

摘要

The uniformity of panchromatic cathodoluminescence (CL) from In0.09Ga0.91N/GaN quantum wells at 100 K was investigated using a combined transmission electron microscope-cathodoluminescence instrument. A technique for correcting CL images of electron-transparent wedge specimens for thickness contrast artefacts is presented. The foil thickness was estimated using the dynamical formulation of the relationship between the thickness and the (experimentally observed) transmitted electron intensity. For a given thickness the CL intensity was calculated using the Everhart-Hoff depth-dose function and also taking into account surface recombination losses. Experimental CL images were normalized by dividing by the calculated CL value at each point. The procedure was successful in calculating the underlying materials contrast in CL images of thin specimens of InGaN single quantum wells. Non-uniformities in the CL emission on the scale of similar to0.7 mum were observed.