Revelation of dislocations in HVPE GaN single crystal by KOH etching with Na2O2 additive and cathodoluminescence mapping

Threading dislocations have been studied by means of etch pit method using molten KOH + Na2O2 solution, cathodoluminescence and transmission electron microscopy. We focus on the geometrical features of etch pits and their correlation with the recombination behavior at the dislocations. Four types of etch pits can be recognized after etching according to their sizes and depths, among which the middle-sized etch pits correspond to dislocations with the strongest non-radiative recombination. TEM observation has confirmed that dislocation beneath the large-sized etch pit is a mixed-type dislocation having both c- and a-component.