Electronic structure of threading dislocations in wurtzite GaN

Abstract

We have carried out atomistic simulations, based on density functional theory, to investigate the atomic and electronic structures of the three types of prismatic threading dislocations in hexagonal gallium nitride. Screw and mixed threading dislocations were demonstrated to introduce both deep and shallow gap states, while most of core configurations of the edge dislocation introduce solely shallow states. The higher electrical activity of both screw and mixed dislocations, compared to the edge one, is correlated with the high dispersion of their energy levels, within the GaN bandgap. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Core properties and mobility of the basal screw dislocation in wurtzite GaN: a density functional theory study

“…From these electronic structures, it is concluded that all three core configurations introduce only shallow energy levels in the GaN band gap. This is contrasted with c-type prismatic screw dislocations which induce both shallow and deep gap states [25,50,51].…”

“…However, the formation of wrong bonds can be in some cases energetically beneficial and then occurs in ground state core configurations in GaN. This is the case of the core configuration with a 5/7-atom rings structure of the a-type edge dislocation [50,51]. Very few reports exist in literature concerning the energetics of basal screw dislocations in hexagonal covalent materials.…”

“…From these electronic structures, it is concluded that all three core configurations introduce only shallow energy levels in the GaN band gap. This is contrasted with c-type prismatic screw dislocations which induce both shallow and deep gap states[25,50,51].For the configuration (S ), the occupied energy levels are introduced in the GaN band gap between E v and E v + 0.2 eV (figure5(a)), where E v represents the valence band maximum. The unoccupied energy levels are ranging from E c to E c − 0.3 eV (figure 5(a)), where E c stands for the conduction band minimum.…”

Impact of screw and edge dislocations on the thermal conductivity of individual nanowires and bulk GaN: a molecular dynamics study

“…[34][35][36] Similarly, for the screw dislocation, the single 6-atom ring (S6S) configuration is formed when the origin of the displacement field is positioned on the IV point, while when the origin is located on the I point, the double 6-atom ring configuration (D6S) is constructed. 37,38 Initially, very large supercell-cluster hybrids of about 30 000 atoms containing an edge or a screw dislocation were constructed. ‡ For the edge dislocation, we modeled the 4E, 5/7E and the 8E configurations, while for the screw dislocation, we considered Fig.…”

“…It is proved that, concerning the edge dislocation: the 4-atom ring (4E), 5/7-atom ring (5/7E) and 8-atom ring (8E) core atomic configurations are formed when the origin of the displacement field at the positions I, II and III respectively [33,34,35]. Similarly for the screw dislocation, the single 6-atom ring (S6S) configuration is formed when the origin of the displacement field is positioned on the IV point, while when the origin is located on the I point, the double 6-atom ring configuration (D6S) is constructed [36,37].…”