Theoretical and Experimental Analysis of Optical Properties of Defects in GaN -
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2017-01-01 |
| Journal | VCU Scholars Compass (Virginia Commonwealth University) |
| Authors | I. C. Diallo |
Abstract
Section titled āAbstractāUsing the Heyd-Scuseria-Ernzherof (HSE06) hybrid functional method along with photoluminescence experimental measurements, we analyze the properties of intrinsic defects such as vacancies, interstitials, antisites, and common complexes. By using configurational coordinate diagrams, we estimate the likelihood of defects to be radiative or non-radiative. Our calculations show that gallium vacancies exhibit a large magnetic moment in the neutral charge state and are most likely non-radiative. We also investigate the correlation between the observed infrared PL bands created in 2.5 MeV electron-irradiated GaN samples and the formation of native defects. It is found that gallium-nitrogen divacancies are possible sources of the broad PL band peaking at 0.95 eV while interstitial gallium is likely to be responsible for the narrow infrared PL band centered around 0.85 eV, with a phonon fine structure at 0.88 eV.\nIn addition to native defects, we also investigate the blue luminescence band (BL2) peaking at 3.0 eV that is observed in high-resistivity GaN samples. Under extended ultraviolet (UV) light exposure, the BL2 band transforms into the yellow luminescence (YL) band with a maximum at 2.2 eV. Our calculations suggest that the BL2 band is related to a hydrogen-carbon defect complex, either CNON-Hi or CN-Hi. The complex creates defect transition level close to the valence band, which is responsible for the BL2 band. Under UV illumination, the complex dissociates, leaving as byproduct the source of the YL band (CNON or CN) and interstitial hydrogen.\nIn conclusion, theoretical predictions of thermodynamic and optical transitions of defects in GaN via the HSE06 method, are found to be within less than 0.2 eV when compared to experiment. Hence the HSE formalism is a powerful tool for the identification and characterization of defects responsible for observed PL bands in GaN.