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Title: Cathodoluminescence studies of carrier concentration dependence for the electron-irradiation effects in p-GaN

Abstract

Electron-irradiation increase of nonequilibrium carrier lifetime was studied as a function of hole concentration in Mg-doped GaN. Temperature-dependent cathodoluminescence (CL) studies yielded activation energies of 344, 326, 237, and 197 meV for samples with hole concentrations of 2x10{sup 16}, 9x10{sup 16}, 3x10{sup 18}, and 7x10{sup 18} cm{sup -3}, respectively. The systematic decay of activation energy with carrier concentration was found to be consistent with Mg acceptors, indicating the involvement of the latter levels in irradiation-induced lifetime changes.

Authors:
; ; ; ; ; ;  [1];  [2];  [3]
  1. University of Central Florida, Orlando, Florida 32816-2385 (United States)
  2. (United States)
  3. (Israel)
Publication Date:
OSTI Identifier:
20971875
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 90; Journal Issue: 17; Other Information: DOI: 10.1063/1.2733620; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ACTIVATION ENERGY; CARRIER DENSITY; CARRIER LIFETIME; CATHODOLUMINESCENCE; DOPED MATERIALS; GALLIUM NITRIDES; HOLES; IRRADIATION; MAGNESIUM; SEMICONDUCTOR MATERIALS; TEMPERATURE DEPENDENCE

Citation Formats

Lopatiuk-Tirpak, O., Chernyak, L., Wang, Y. L., Ren, F., Pearton, S. J., Gartsman, K., Feldman, Y., University of Florida, Gainesville, Florida 32611, and Weizmann Institute of Science, Rehovot 76100. Cathodoluminescence studies of carrier concentration dependence for the electron-irradiation effects in p-GaN. United States: N. p., 2007. Web. doi:10.1063/1.2733620.
Lopatiuk-Tirpak, O., Chernyak, L., Wang, Y. L., Ren, F., Pearton, S. J., Gartsman, K., Feldman, Y., University of Florida, Gainesville, Florida 32611, & Weizmann Institute of Science, Rehovot 76100. Cathodoluminescence studies of carrier concentration dependence for the electron-irradiation effects in p-GaN. United States. doi:10.1063/1.2733620.
Lopatiuk-Tirpak, O., Chernyak, L., Wang, Y. L., Ren, F., Pearton, S. J., Gartsman, K., Feldman, Y., University of Florida, Gainesville, Florida 32611, and Weizmann Institute of Science, Rehovot 76100. Mon . "Cathodoluminescence studies of carrier concentration dependence for the electron-irradiation effects in p-GaN". United States. doi:10.1063/1.2733620.
@article{osti_20971875,
title = {Cathodoluminescence studies of carrier concentration dependence for the electron-irradiation effects in p-GaN},
author = {Lopatiuk-Tirpak, O. and Chernyak, L. and Wang, Y. L. and Ren, F. and Pearton, S. J. and Gartsman, K. and Feldman, Y. and University of Florida, Gainesville, Florida 32611 and Weizmann Institute of Science, Rehovot 76100},
abstractNote = {Electron-irradiation increase of nonequilibrium carrier lifetime was studied as a function of hole concentration in Mg-doped GaN. Temperature-dependent cathodoluminescence (CL) studies yielded activation energies of 344, 326, 237, and 197 meV for samples with hole concentrations of 2x10{sup 16}, 9x10{sup 16}, 3x10{sup 18}, and 7x10{sup 18} cm{sup -3}, respectively. The systematic decay of activation energy with carrier concentration was found to be consistent with Mg acceptors, indicating the involvement of the latter levels in irradiation-induced lifetime changes.},
doi = {10.1063/1.2733620},
journal = {Applied Physics Letters},
number = 17,
volume = 90,
place = {United States},
year = {Mon Apr 23 00:00:00 EDT 2007},
month = {Mon Apr 23 00:00:00 EDT 2007}
}
  • The electron irradiation-induced increase of minority carrier diffusion length was studied as a function of hole concentration in Mg-doped GaN. Variable-temperature electron beam induced current measurements yielded activation energies of 264, 254, 171, and 144 meV for samples with hole concentrations of 2x10{sup 16}, 9x10{sup 16}, 3x10{sup 18}, and 7x10{sup 18} cm{sup -3}, respectively. This carrier concentration dependence of the activation energy for the effects of electron irradiation was found to be consistent with Mg acceptors, indicating the involvement of the latter levels in the irradiation-induced diffusion length increase.
  • Here, 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 wafer-scale, 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 2.5 MeV protons at fluences of 4–6 × 10 13 protons/cm 2. We also characterize themore » 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 (V Ga-related), carbon impurities (C-related), and gallium interstitials (Ga i). EBIC imaging suggests long-range migration and clustering of radiation-induced point defects over distances of ~500 nm, which suggests mobile Ga i. 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 Ga i.« less
  • Micron-scale mapping has been employed to study a contacted InGaN/GaN LED using combined electroluminescence (EL), cathodoluminescence (CL), and electron beam induced current (EBIC). Correlations between parameters, such as the EBIC and CL intensity, were studied as a function of applied bias. The CL and EBIC maps reveal small areas, 2–10 μm in size, which have increased nonradiative recombination rate and/or a lower conductivity. The CL emission from these spots is blue shifted, by 30–40 meV. Increasing the reverse bias causes the size of the spots to decrease, due to competition between in-plane diffusion and drift in the growth direction. EL mapping showsmore » large bright areas (∼100 μm) which also have increased EBIC, indicating domains of increased conductivity in the p and/or n-GaN.« less
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