Contrast analysis of dislocation images in TEM-cathodoluminescence technique

Monochromatic cathodoluminescence CL images of the threading dislocations in Si-doped n-GaN were observed by the TEM-CL technique. We studied dependence of the contrast and the FWHM of the dislocation image on sample thickness, accelerating voltage and temperature. The CL spectra were measured at various temperatures and were analyzed to find the property of the band edge (BE) emission used for the CL imaging. The observation showed that the FWHM of the dislocation contrast monotonically increases with sample thickness and decreases with accelerating voltage, which qualitatively agrees with the behavior expected from the theory. On the other hand, the temperature dependence of the FWHM shows an anomalous behavior. This dependence can be explained by the mobility and lifetime of holes as a function of temperature. The relation between the FWHM of the dislocation contrast and the diffusion length is also discussed.