Characterizing nanometer-sized V-defects in InGaN single quantum well films by high-spatial-resolution cathodoluminescence spectroscopy

We studied cathodoluminescence (CL) spectral variations in the vicinity of the V-defects in InGaN single quantum well (SQW) films by using our newly developed SE-SEM-CL. The peak intensity and peak wavelength of the CL peaks around 448 and 400 nm were found to change significantly near the apex of a V-defect. These variations were mainly attributed to a change in the In content of the InGaN SQW layer in the sidewalls and apex of the V-defect. Furthermore, an abnormal change was observed in the CL peak at 365 nm near the apex of the V-defect; this change was mainly caused by the stress induced by a force at the film edge that results from the thermal expansion differences between the film and the GaN layer. On the basis of the obtained results, we proposed a model of the formation of V-defects by selective termination of the threading defects on the (0001) surface of pseudomorphic InGaN SQW and GaN buffer layers by In.