Dislocations in GaN single crystals were studied by means of spectral cathodoluminescence mapping and defect selective etching. It was shown that the c-type screw dislocations were not recombination active. The recombination strength of the a- and (a+c)-type dislocations was influenced by impurity gettering. While fresh dislocations exhibited a cathodoluminescence contrast of 0.01 to 0.05 in accord with intrinsic dislocation states, grown-in dislocations exhibited a contrast of 0.25. From the analysis of spectral cathodoluminescence maps, it was found that impurities such as O and Si were depleted in the surroundings of the dislocations. The increased contrast due to a reduced screening of the electrical field of the dislocation was explained.

Nonradiative Recombination at Threading Dislocations in n-Type GaN - Studied by Cathodoluminescence and Defect Selective Etching. M.Albrecht, J.L.Weyher, B.Lucznik, I.Grzegory, S.Porowski: Applied Physics Letters, 2008, 92[23], 231909