Effect of Vacancy Defects on the Electronic Structure and Optical Properties of GaN

The effect of gallium vacancy (VGa) and nitrogen vacancy (VN) defects on the electronic structure and optical properties of GaN using the generalized gradient approximation method within the density functional theory were investigated. The results show that the band gap increases in GaN with vacancy defects. Crystal parameters decrease in GaN with nitrogen vacancy (GaN:VN) and increase in GaN with gallium vacancy (GaN:VGa). The Ga vacancy introduces defect levels at the top of the valence band, and the defect levels are contributed by N2p electron states. In addition, the energy band shifts to lower energy in GaN:VNand moves to higher energy in GaN:VGa. The level splitting is observed in the N2p states of GaN:VNand Ga3d states of GaN:VGa. New peaks appear in lower energy region of imaginary dielectric function in GaN:VNand GaN:VGa. The main peak moves to higher energy slightly and the intensity decreases.

COMPLEXES OF SPATIALLY MULTISTABLE DEFECTS AS THE SOURCE OF 1/f NOISE IN GaAs DEVICES

In order to determine the origin of 1/f noise in devices made on the basis of GaAs the structure and spatial multistability mechanism of complexes of defects originated by donor–acceptor pairs are researched. Examples of complexes, which potentially exist in n- GaAs : Si , are such pairs as SiAsSiGa , VGaSiGa , VGaVAs , VAsSiAs and VGaISi . For instance, VGaSiGa complex contains a gallium vacancy (VGa) and an atom of silicon (SiGa), which substitutes the nearest atom of gallium in the crystal lattice. The mechanism of spatial multistability of the entire complex of defects is linked with the influence of the Jahn–Teller effect on the complex or one of its elements. The ability of VGaSiGa complex to be one of the sources of 1/f noise is analyzed. It is assumed that 1/f noise may be generated by defects influenced by the Jahn–Teller effect.