Strain Induced Deep Electronic States around Threading Dislocations in GaN

Abstract

Combining through-focus high-resolution transmission electron microscopy and hierarchical multiscale simulations consisting of density-functional theory, analytical empirical potentials, and continuum elastic theory we demonstrate the existence of a new dislocation type in GaN. In contrast with all previously identified or suggested dislocation structures in GaN, all core atoms are fully coordinated; i.e., no broken bonds occur, implying that the dislocation should be electrically inactive. However, as we show, the giant local strain-field around the dislocation core, in combination with the small lattice constant of GaN, causes deep defect states and thus electrically active edge dislocations independent on the specific core structure.

Point defect segregation and its role in the detrimental nature of Frank partials inCu(In,Ga)Se2thin-film absorbers

“…Moreover, although there are no dangling bonds in the stoichiometric structures, defect levels are also observed in the LDOS of the stoichiometric structures. We argue that they are strain induced, similar to what has been observed in the case of threading dislocations in GaN 28 . In order to elucidate the nature of the Cu clouds detected around the cores (Fig.…”

Segregation of In to Dislocations in InGaN

“…These dislocations can severely degrade device efficiencies 2 , and lifetimes 3 and are responsible for a broad range of undesirable behavior such as leakage currents 4 and properties such as reduced internal quantum efficiencies 5 and defect states 6,7,8,9,10 that can act as non-radiative recombination centers. In x Ga 1-x N-based alloy semiconductors are used in light-emitting diodes 11 , laser diodes 12 and solar cells 13 , which can be tuned to emit or absorb respectively over the entire visible spectrum by varying the In composition 14 .…”

Kinetic path towards the passivation of threading dislocations in GaN by oxygen impurities

“…These observations raise the question: can interaction with O offer a clue to the exceptional dislocation tolerance of GaN? Since the most common type of dislocation observed for c-plane growth in GaN is the threading edge dislocation [23], among which the 5/7-atom ring core structure, with alternating Ga-Ga and N-N homopolar (wrong) bonds, is found to be experimentally and theoretically most stable [24][25][26], the question then becomes: will unintentional O passivate the edge dislocations? Clearly, the answer to such a question can be important to GaN and other vital optoelectronic materials.…”