Effect of dislocations on luminescence properties of silicon-doped GaN grown by metalorganic chemical vapor deposition method

Abstract

The effect of dislocations on the structural and electro-optic characteristics of n-GaN has been studied. X-ray diffraction, Hall measurement, photoluminescence spectroscopy, Raman spectroscopy, and transmission electron microscopy (TEM) have been performed to understand the interdependence of strain, dislocation, and doping concentration. The most remarkable observation of the study is the blueshift observed at a doping level ND∼1018 cm−3 as a result of the relaxation of strain. The TEM results reveal a higher dislocation defect density at lower doping levels (∼1017 cm−3) than at moderate doping levels. Blueshift is found to result from the redistribution of the dislocation density due to the reduction in strain at a certain optimum doping level(s). This distribution of the dislocation is such that there are virtually no dislocations at some locations, as evident from the sample MD27 with doping ⩾1018 cm−3.