Münster 1999 – scientific programme
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HL: Halbleiterphysik
HL 23: Poster II
HL 23.68: Poster
Wednesday, March 24, 1999, 14:00–18:00, Z
THE INTERACTION OF OXYGEN WITH THREADING EDGE AND SCREW DISLOCATIONS IN GAN — •Joachim Elsner1, Michael Haugk2, Rafael Gutierrez1, and Thomas Frauenheim2 — 1TU Chemnitz, Institut für theoret. Physik III, 09107 Chemnitz — 2Universität GH Paderborn, Fb. 6, 33098 Paderborn
Local density functional methods are used to determine the atomic geometries, electrical properties and line energies of threading edge and screw dislocations in GaN. Both these types of dislocation were constructed using elasticity theory. In the impurity free edge dislocation the core structure is similar to that found for the (10-10) surface leading to a gap free from deep levels. However, we find that it is energetically favourable for defects, such as the Ga vacancy, O and related complexes to be trapped at the core region of the threading edge dislocation. It has been suggested that such defects are correlated with the yellow luminescence band in GaN. The screw dislocation with a filled core possesses strained states but a screw with an open core is free from gap states. Oxygen has a strong tendency to migrate to the (10-10) surface. Theory identifies another Ga vacancy O defect complex to be particularly stable and electrically inert. In growing crystallites it is suggested that these defects segregate to the surfaces where grains meet. As crystalline growth proceeds the area of the cavity surface contracts leading to an increased defect density that inhibit further growth and prevent the filling-in of the cavity thus creating a nanopipe.