Electronic Structures and Magnetic Properties of GaN Sheets and Nanoribbons

First principles calculations were performed to study the electronic structures of gallium nitride (GaN) sheets and nanoribbons (NRs) in order to understand the influence of defects or edge states on magnetic properties. It is shown that the Ga-defective GaN sheet may be a good candidate for spintronics due to its half-metal property under certain conditions, even if a perfect GaN sheet is a nonmagnetic semiconductor. We investigated both zigzag and armchair GaN NRs with and without edge atoms passivated by H. The H-passivated GaN NRs and bare armchair NRs can be classified as nonmagnetic semiconductors. Band gap gradually decreases with the increase of the width of NRs. A ferromagnetic character occurs in bare zigzag GaN NRs with width of about 1.7 nm (mainly determined by edge Ga and N). Furthermore, we have shown that thin layer GaN NRs could also be ferromagnetic. Magnetic moment does not decrease to zero even up to six layers. Results offer a deeper understanding of the influence of both defects and edge states of GaN sheets and monolayer and multilayer NRs, particularly in terms of their structural and magnetic properties.