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Proceedings Paper

Optical properties of polar, nonpolar, and semipolar InGaN/GaN multiple quantum wells on sapphire
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Paper Abstract

The polarization fields in the c-axis-oriented hexagonal GaN system cause spatial separation of electrons and holes in quantum wells, reducing the quantum efficiency, and resulting in a red shift of the emission as well as a blue shift with increasing injected carrier density. In this paper, we report on the growth and optical characterization of InGaN/GaN multiple quantum wells (MQWs) on nonpolar (112¯0) a- and polar (0001) c-planes, as well as two semipolar planes, (112¯2) and (11¯01) of GaN. There are two kinds of a-plane used in this study. One of the (112¯0) a-planes was obtained on (11¯00) m-plane sapphire substrates during the epitaxial lateral overgrowth (ELO) of (112¯2) oriented semipolar GaN films, while the other one was planar a-plane GaN which was grown on (11¯01) r-plane sapphire substrates. The semipolar (112¯2) and (11¯01) planes were obtained as sidewall facets during the ELO of c-plane GaN with the mask stripes aligned along the GaN m-axis and a-axis, respectively. InGaN/GaN multiple quantum wells (MQWs) with a nominal well thickness of 4 nm and a barrier thickness of 8 nm were grown on these five GaN samples by metalorganic chemical vapor deposition. Excitation power dependent photoluminescence (PL) measurements were carried out on these quantum well structures to study the effect of polarization-induced electric field on the band-edge emission. The quantum-well emission energy from the two a-plane MQWs showed zero shift, compared to a 74 meV blue shift for the c-plane MQWs when the excitation power was increased from 1.3 mW to 37.0 mW. The semipolar (112¯2) showed a blue shift of 35 meV with increased excitation power, suggesting reduced polarization compared to that of c-plane. No quantum-well emission could be observed for the MQWs on (11¯01) semipolar planes. The shift in the quantum-well emission energy was attributed to the change of the screening effect of photon-generated carriers in the quantum wells at different excitation powers. For exact notation please see manuscript

Paper Details

Date Published: 15 February 2008
PDF: 6 pages
Proc. SPIE 6894, Gallium Nitride Materials and Devices III, 689428 (15 February 2008); doi: 10.1117/12.763260
Show Author Affiliations
X. Ni, Virginia Commonwealth Univ. (United States)
R. Shimada, Virginia Commonwealth Univ. (United States)
J. H. Leach, Virginia Commonwealth Univ. (United States)
J. Xie, Virginia Commonwealth Univ. (United States)
Ü. Özgür, 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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