Browsing by Author "Tzou, A. J."

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Improved carrier injection in GaN-based VCSEL via AlGaN/GaN multiple quantum barrier electron blocking layer
(2015-10-19)
Hsieh, D. H.
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Tzou, A. J.
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Kao, T. S.
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Lai, F. I.
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Lin, D. W.
In this report, the improved lasing performance of the III-nitride based vertical-cavity surface-emitting laser (VCSEL) has been demonstrated by replacing the bulk AlGaN electron blocking layer (EBL) in the conventional VCSEL structure with an AlGaN/GaN multiple quantum barrier (MQB) EBL. The output power can be enhanced up to three times from 0.3 mW to 0.9 mW. In addition, the threshold current density of the fabricated device with the MQB-EBL was reduced from 12 kA/cm(2) (9.5 mA) to 10.6 kA/cm(2) (8.5 mA) compared with the use of the bulk AlGaN EBL. Theoretical calculation results suggest that the improved carrier injection efficiency can be mainly attributed to the partial release of the strain and the effect of quantum interference by using the MQB structure, hence increasing the effective barrier height of the conduction band. (C) 2015 Optical Society of America
Optical properties of Zn1-xMnxO thin films grown by molecular beam epitaxy
(2013-09-01)
Chien, K. F.
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Yang, Y. L.
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Tzou, A. J.
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Chou, W. C.
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電子物理學系
Zn(1-x)Mn(x)0 (x=0-0.061) thin films were grown by molecular beam epitaxy (MBE) system. Transmittance shows an increase of the band gap with the increasing Mn concentration. Resonant Raman scattering (RRS) spectra showed 11 longitudinal optical phonon lines for the Zn1-xMnxO samples. For the Zn0.997Mn0.003O sample, circular polarization degree of 9% was observed at magnetic field B=5 T. The dependence of circular polarization rate on the magnetic field intensity exhibits Brillouin type para-magnetism. (c) 2012 Elsevier B.V. All rights reserved.
The study of self-assembled ZnO nanorods grown on Si(111) by plasma-assisted molecular beam epitaxy
(2013-09-01)
Tzou, A. J.
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Chien, K. F.
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Lai, H. Y.
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Ku, J. T.
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Lee, L.
The growth and optical properties of self-assembled ZnO nanorods grown on Si(111) substrate by plasma-assisted molecular beam epitaxy (PA-MBE) were studied. By controlling the Zn/O flux ratio, the growth of ZnO nanorods on Si(111) substrate without catalyst has been achieved. Scanning electron microscopy (SEM) shows the ZnO nanorods with various density and diameter could be controlled. Photoluminescence (PL) measurements exhibit nice optical properties. The sharp near band edge PL emission with full width at half maximum (FWHM) of about 17 meV indicates that the ZnO nanorods could be used as the high efficient photonic devices. Crown Copyright (c) 2013 Published by Elsevier B.V. All rights reserved.