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Proceedings Paper

Comparative study of deep levels in GaN grown on different templates
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Paper Abstract

Deep levels in thin GaN epilayers grown by metal-organic chemical vapor deposition on different templates were studied by photocapacitance spectroscopy and deep-level transient spectroscopy (DLTS) using Schottky barrier diodes. We observed the reduction of electrically and optically active traps in GaN grown with in situ SiNx nanonetwork and SiO2 striped mask or conventional epitaxial lateral overgrowth technique (ELO) as compared to a typical control layer on a sapphire substrate. All samples measured by DLTS in the temperature range from 80 K to 400 K exhibited traps with activation energies 0.55-0.58 eV and 0.21-0.28 eV. The lowest concentration of both traps was achieved for the sample with 6 min deposition of SiNx nanonetwork, which was lower than that for the sample prepared by conventional ELO, and much lower than that in the control. The steady-state photocapacitance spectra of all samples taken at 80 K over the spectral range 0.75-3.50 eV demonstrated a similar trend for all the layers. The photocapacitance spectra exhibited defect levels with optical threshold energies of 1.2-1.3, 1.6, 2.2 and 3.1 eV. The determined concentrations of traps were compared and the results were consistent with DLTS measurements. The layer with SiNx nanonetwork has the lowest concentrations of optically active traps with the standard GaN control layer being the worst in terms of trap concentrations. The consistent trend among the photocapacitance spectroscopy and DLTS results suggests that SiNx network can effectively reduce deep levels in GaN, which otherwise can deteriorate both optical and electrical performance of GaN-based devices.

Paper Details

Date Published: 15 February 2008
PDF: 10 pages
Proc. SPIE 6894, Gallium Nitride Materials and Devices III, 689424 (15 February 2008); doi: 10.1117/12.767834
Show Author Affiliations
J. Nie, Virginia Commonwealth Univ. (United States)
S. A. Chevtchenko, Virginia Commonwealth Univ. (United States)
J. Xie, Virginia Commonwealth Univ. (United States)
X. Ni, Virginia Commonwealth Univ. (United States)
H. Morkoç, Virginia Commonwealth Univ. (United States)

Published in SPIE Proceedings Vol. 6894:
Gallium Nitride Materials and Devices III
Hadis Morkoç; Cole W. Litton; Jen-Inn Chyi; Yasushi Nanishi; Euijoon Yoon, Editor(s)

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