Nonradiative recombination at threading dislocations in n-type GaN: Studied by cathodoluminescence and defect selective etching

Abstract

Dislocations in GaN single crystal were studied by means of spectral cathodoluminescence (CL) mapping and defect selective etching. We show that the c-type screw dislocations are not recombination active. The recombination strength of the a- and (a+c)-type dislocations is influenced by impurity gettering. While fresh dislocations exhibit a CL contrast of 0.01–0.05 in accordance with intrinsic dislocation states, grown in dislocations show a contrast of 0.25. From the analysis of spectral CL maps, we find that impurities such as oxygen and silicon are depleted in the surrounding of the dislocations. We explain the increased contrast by a reduced screening of the electrical field of the dislocation.