کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
9845035 | 1645433 | 2005 | 6 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Defect attributed variations of the photoconductivity and photoluminescence in the HVPE and MOCVD as-grown and irradiated GaN structures
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
فیزیک و نجوم
ابزار دقیق
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
The effect of native and radiation induced defects on the photoconductivity transients and photoluminescence spectra have been examined in GaN epitaxial layers of 2.5 and 12 μm thickness grown on bulk n-GaN/sapphire substrates by metal-organic chemical vapor deposition (MOCVD). For comparison, free-standing GaN as-grown samples of 500 μm thickness, fabricated by hydride vapor phase epitaxy (HVPE), were investigated. Manifestation of defects induced by 10-keV X-ray irradiation with the dose of 600 Mrad and 100-keV neutrons with the fluences of 5Ã1014 and 1016 cmâ2 as well as of 24 GeV/c protons with fluence 1016 cmâ2 have been revealed through contact photoconductivity and microwave absorption transients. The amplitude of the initial photoconductivity decay is significantly reduced by the native and radiation defects density. Synchronous decrease of the steady-state PL intensity of yellow, blue and ultraviolet bands peaked at 2.18, 2.85, and 3.42 eV, respectively, with density of radiation-induced defects is observed. The decrease of the PL intensity is accompanied by an increase of asymptotic decay lifetime in the photoconductivity transients, which is due to excess-carrier multi-trapping. The decay fits the stretched exponent approximation exp[-(t/Ï)α] with the different factors α in as-grown material (αâ0.7) and irradiated samples (αâ0.3). The fracton dimension ds of disordered structure changes from 4.7 to 0.86 for as-grown and irradiated material, respectively, and it implies the percolative carrier motion on an infinite cluster of dislocations net in the as-grown material and cluster fragmentation into finite fractons after irradiations.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment - Volume 552, Issues 1â2, 21 October 2005, Pages 82-87
Journal: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment - Volume 552, Issues 1â2, 21 October 2005, Pages 82-87
نویسندگان
E. Gaubas, P. Pobedinskas, J. Vaitkus, A. Uleckas, A. Žukauskas, A. Blue, M. Rahman, K.M. Smith, E. Aujol, B. Beaumont, J.-P. Faurie, P. Gibart,