First-principles analysis of the optoelectronic properties of defective gallium nitride (Conference Presentation)

Abstract

III-Nitrides form a class of wide bandgap semiconductors that have broad applications in optoelectronics technology due to their relatively large band gap, high carrier drift velocity and high breakdown voltage. In particular, GaN and its alloys are promising as component materials in solid-state lighting, radio-frequency, and power electronics. However, these materials generally grow with high defect densities, which can substantially degrade their electronic and optical properties. Therefore, an accurate and detailed knowledge of the influence of defects on their electronic structure will be central to the design of new high-performance materials. Here, we take a density functional theory (DFT) and many-body perturbation theory (MBPT) approach to describe the excited-states of defective GaN. Utilizing MBPT within the GW/BSE approximation, we develop an approach to systematically identify defects, and their associated trap state energies. For a +1 charged nitrogen vacancy within bulk GaN, the predicted bandstructure indicates that this particular defect results in the formation of shallow defect states with trap state energies near the band edges. However, analysis of the electron-hole correlation function reveals that the low-energy excitations are comprised of a mixed bulk-like and defect-like character with significant exciton binding energies (~ 0.1 eV). We discuss the implications of these defect-induced-states for the electron transport and optical properties of GaN.