부산대학교 도서관

Inherent advantages of wide bandgap materials make GaN-based devices attractive for power electronics and applications in radiation environments. Recent advances in the availability of waferscale, bulk GaN substrates have enabled the production of high quality, low defect density GaN devices, but fundamental studies of carrier transport and radiation hardness in such devices are lacking. Here, we report measurements of the hole diffusion length in low threading dislocation density (TDD), homoepitaxial n-GaN, and high TDD heteroepitaxial n-GaN Schottky diodes before and after irradiation with 2.5MeV protons at fluences of 4–6 X 10-13 protons/cm2. We also characterize the specimens before and after irradiation using electron beam-induced-current (EBIC) imaging, cathodoluminescence, deep level optical spectroscopy (DLOS), steady-state photocapacitance, and lighted capacitance-voltage (LCV) techniques. We observe a substantial reduction in the hole diffusion length following irradiation (50%–55%) and the introduction of electrically active defects which could be attributed to gallium vacancies and associated complexes (VGa-related), carbon impurities (C-related), and gallium interstitials (Gai). EBIC imaging suggests long-range migration and clustering of radiation-induced point defects over distances of ~500 nm, which suggests mobile Gai. Following irradiation, DLOS and LCV reveal the introduction of a prominent optical energy level at 1.9 eV below the conduction band edge, consistent with the introduction of Gai. [ABSTRACT FROM AUTHOR]