Browsing by Author "Lin, Woei-Tyng"

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Characterization of large area Cu(In,Ga)Se-2 nanotip arrays via photoluminescence
(2012)
Liao, Yu-Kuang
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Lin, Woei-Tyng
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Hsieh, Dan-Hua
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Kuo, Shou-Yi
;
Lai, Fang-I
In this study, photoluminescence (PL) measurements were used to characterized Cu(In,Ga)Se-2 nanotip arrays (CIGS NTRs). Large area CIGS NTRs were yielded by using one step Ar+ milling process without template. Formation mechanism of NTRs is due to a highly anisotropic milling effect of the quaternary components compound. In both CIGS thin films with and without NTRs, saturation effects of Donor-Acceptor Pair (DAP) had been observed while excitation power dependence PL measurements. Comparing with thin film CIGS without NTRs, it has revealed that the concentration DAP had been changed after formation of CIGS NTRs and had enhanced its carrier density of the p-type semiconductor.
Heteroepitaxial growth of InN on GaN intermediate layer by PA-MOMBE
(2011-07-01)
Lai, Fang-I
;
Kuo, Shou-Yi
;
Chen, Wei-Chun
;
Lin, Woei-Tyng
;
Wang, Wei-Lin
In this paper, high-quality wurtzite indium nitride was epi-grown on sapphire substrates by plasma-assisted metal-organic molecule beam epitaxy system (PA-MOMBE). Structural and electrical properties of the InN films were significantly improved by employing a GaN buffer layer. In addition, high-resolution X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy (TEM), Hall Effect, Raman and photoluminescence spectroscopy were carried out to characterize the effect of the growth temperature on structural and optoelectronic properties. It was found that highly c-axis oriented InN epilayer can be obtained by optimizing growth conditions. TEM images reveal that the epitaxially grown InN/GaN interface is sharp, and the spacing of the InN(0 0 0 2) lattice plane is about 0.57 nm. Raman spectra also show a sharp peak at 491 cm(-1) attributed to the E(2)(high) mode of wurtzite InN. These results indicate that the improvement of InN material quality can be achieved using heteroepitaxy on GaN/sapphire templates. (C) 2011 Elsevier B.V. All rights reserved.
Observation of unusual optical transitions in thin-film Cu(In,Ga)Se-2 solar cells
(2012-11-05)
Liao, Yu-Kuang
;
Kuo, Shou-Yi
;
Lin, Woei-Tyng
;
Lai, Fang-I
;
Hsieh, Dan-Hua
In this paper, we examine photoluminescence spectra of Cu(In,Ga)Se-2 (CIGS) via temperature-dependent and power-dependent photoluminescence (PL). Donor-acceptor pair (DAP) transition, near-bandedge transition were identified by their activation energies. S-shaped displacement of peak position was observed and was attributed to carrier confinement caused by potential fluctuation. This coincides well with the obtained activation energy at low temperature. We also present a model for transition from V-Se to V-In and to V-Cu which illustrates competing mechanisms between DAPs recombinations. (C) 2012 Optical Society of America
Study of InN epitaxial films and nanorods grown on GaN template by RF-MOMBE
(2012-08-21)
Chen, Wei-Chun
;
Kuo, Shou-Yi
;
Wang, Wei-Lin
;
Tian, Jr-Sheng
;
Lin, Woei-Tyng
This paper reports on high-quality InN materials prepared on a GaN template using radio-frequency metalorganic molecular beam epitaxy. We also discuss the structural and electro-optical properties of InN nanorods/films. The X-ray diffraction peaks of InN(0002) and InN(0004) were identified from their spectra, indicating that the (0001)-oriented hexagonal InN was epitaxially grown on the GaN template. Scanning electron microscopic images of the surface morphology revealed a two-dimensional growth at a rate of approximately 0.85 mu m/h. Cross-sectional transmission electron microscopy images identified a sharp InN/GaN interface and a clear epitaxial orientation relationship of [0001](InN) // [0001](GaN) and ((2) over bar 110)(InN) // ((2) over bar 110)(GaN). The optical properties of wurtzite InN nanorods were determined according to the photoluminescence, revealing a band gap of 0.77 eV.