Browsing by Author "Lin, D. Y."

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A comprehensive study of temperature-dependent reflectance and photoluminescence of Zn(1-x)Mn(x)O thin films grown on c-Al(2)O(3)
(2009-03-01)
Lin, D. Y.
;
Lin, H. J.
;
Wu, J. S.
;
Chou, W. C.
;
Yang, C. S.
We present a systematic study of temperature-dependent reflectance (R) and photoluminescence (PL) measurements on ZnMnO films grown by plasma-assisted molecular beam epitaxy. For the first time, the three free-exciton transitions FX(A) (Gamma(7c)-Gamma(u)(7v)), FX(B) (Gamma(7c)-Gamma(9v)), and FX(C) (Gamma(7c)-Gamma(l)(7v)) and the longitudinal-optical phonon replicas of FX(B) and FX(C) of ZnMnO films have been clearly observed in the R spectra. The parameters describing the activation energy and the temperature dependence of the transition energy and broadening have been extracted by fitting the experimental R and PL spectra. The spectral data of ZnMnO films not only show the deterioration of crystalline quality with increasing Mn composition fraction but also indicate the Mn clustering caused by Mn atom segregation.
A comprehensive study of temperature-dependent reflectance and photoluminescence of Zn1-xMnxO thin films grown on c-Al2O3
(2009-03-01)
Lin, D. Y.
;
Lin, H. J.
;
Wu, J. S.
;
Chou, W. C.
;
Yang, C. S.
We present a systematic study of temperature-dependent reflectance (R) and photoluminescence (PL) measurements on ZnMnO films grown by plasma-assisted molecular beam epitaxy. For the first time, the three free-exciton transitions FXA (Gamma(7c)-Gamma(u)(7v)), FXB (Gamma(7c)-Gamma(9v)), and FXC (Gamma(7c)-Gamma(l)(7v)) and the longitudinal-optical phonon replicas of FXB and FXC of ZnMnO films have been clearly observed in the R spectra. The parameters describing the activation energy and the temperature dependence of the transition energy and broadening have been extracted by fitting the experimental R and PL spectra. The spectral data of ZnMnO films not only show the deterioration of crystalline quality with increasing Mn composition fraction but also indicate the Mn clustering caused by Mn atom segregation.
Optical characteristics of a-plane ZnO/Zn(0.8)Mg(0.2)O multiple quantum wells grown by pulsed laser deposition
(2010-10-01)
Ko, T. S.
;
Lu, T. C.
;
Zhuo, L. F.
;
Wang, W. L.
;
Liang, M. H.
We reported optical properties of a-plane ZnO/ZnMgO multiple quantum wells (MQWs) structure grown by the pulse laser deposition system. The emission peak energy of a-plane ZnO/ZnMgO MQWs kept invariant in the power-dependent photoluminescence (PL) measurement, indicating the nonpolar characteristics due to the lack of built-in electric fields. Large exciton binding energy of 68 meV was deduced and no apparent S-curve appeared in temperature-dependent PL results, demonstrating less carrier localization effect in a-plane ZnO/ZnMgO MQWs. Large difference in electronic transition levels of 45 meV due to the valence band splitting was observed in the polarization dependent absorption spectrum. Furthermore, the high degree of polarization of 92% and 56% at 20 and 300 K in PL emission of a-plane ZnO/ZnMgO MQWs were obtained. (C) 2010 American Institute of Physics. [doi:10.1063/1.3488898]
Optical characteristics of a-plane ZnO/Zn0.8Mg0.2O multiple quantum wells grown by pulsed laser deposition
(2010-10-01)
Ko, T. S.
;
Lu, T. C.
;
Zhuo, L. F.
;
Wang, W. L.
;
Liang, M. H.
We reported optical properties of a-plane ZnO/ZnMgO multiple quantum wells (MQWs) structure grown by the pulse laser deposition system. The emission peak energy of a-plane ZnO/ZnMgO MQWs kept invariant in the power-dependent photoluminescence (PL) measurement, indicating the nonpolar characteristics due to the lack of built-in electric fields. Large exciton binding energy of 68 meV was deduced and no apparent S-curve appeared in temperature-dependent PL results, demonstrating less carrier localization effect in a-plane ZnO/ZnMgO MQWs. Large difference in electronic transition levels of 45 meV due to the valence band splitting was observed in the polarization dependent absorption spectrum. Furthermore, the high degree of polarization of 92% and 56% at 20 and 300 K in PL emission of a-plane ZnO/ZnMgO MQWs were obtained. (C) 2010 American Institute of Physics. [doi:10.1063/1.3488898]
Optical characterization of Zn0.97Mn0.03Se/ZnSe0.92Te0.08 type II multiple-quantum-well structures
(2007-05-01)
Lin, D. Y.
;
Shiu, J. J.
;
Wu, J. D.
;
Yang, C. S.
;
Chou, W. C.
The optical characterization of type II Zn0.97Mn0.03Se/ZnSe0.92Te0.08 multiple-quantum-well structures have been studied using photoluminescence (PL), temperature-dependent PL, polarized PL, power-dependent PL, and photoreflectance (PR) in this study. The PL data reveal that the band alignment of the ZnMnSe/ZnSeTe system is type II. Comparing with the theoretical calculation based on the Schrodinger equation, the valence band offset is estimated to be 0.6 eV. From the power-dependent PL spectra, it is observed that the peak position of PL spectra shows a blueshift under different excitation power. The blueshift can be interpreted in terms of the band-bending effect due to spatially photoexcited carriers in a type II alignment. The thermal activation energy (E-A) for quenching the PL intensity was determined from temperature-dependent PL spectra. The thermal activation energy was found to decrease as the thickness of ZnMnSe and ZnSeTe layers decreased. The polarized PL spectra exhibit a large in-plane polarization with the polarization degree up to 50%. The polarization does not depend on the excitation intensity as well as temperature. The large polarization is an inherent orientation of the interface chemical bonds. The higher transition features observed in PR spectra show a blueshift with the similar trend observed in the PL spectra as decreasing the thickness of ZnSeTe layer. This result provides a consistent evidence for the assumption that square-like well shapes were built in the ZnSeTe layers. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Optical characterization of ZnMnO thin films on c-Al2O3
(2008-07-01)
Lin, H. J.
;
Lin, D. Y.
;
Wu, J. S.
;
Chou, W. C.
;
Yang, C. S.
Various optical measurement technologies have been used to characterize ZnMnO thin films with different Mn compositions grown by molecular beam epitaxy (MBE) on c-Al2O3 substrates. The lattice constant and the crystalization quality have been evaluated by using X-ray diffraction (XRD). Photoluminescence (PL) has been used to reveal the neutral-donor-bound exciton ((DX)-X-0) and to check the film's quality. Defect-related absorption signatures, in addition to near-band-edge absorption, due to the zinc vacancy and the donor-acceptor pair (DAP) have been found in the surface photovoltage spectra (SPS). Free excitonic transitions and their phonon-assisted replicas have been observed in the reflectance spectra. Our experimental results not only unveil specific optical transition energies but also indicate a rapid material deterioration when Mn incorporation goes beyond a certain amount to cause manganese segregation.
Optical investigation of A-plane ZnO/ZnMgO multiple quantum wells grown by pulsed laser deposition
(2011-12-01)
Lin, D. Y.
;
Huang, T. P.
;
Kao, Y. C.
;
Huang, C. C.
;
Kuo, H. C.
In this study, we present the optical characteristics of A-plane ZnO/ZnMgO multiple quantum wells (MQWs) with different well widths grown on R-plane sapphire substrates by pulsed laser deposition (PLD). The energy gaps of ZnO and ZnMgO have been observed by photoluminescence (PL) and absorption spectra. The electrons confined in the ZnO wells transit from the electron ground sub-band to the heavy-hole ground sub-band (noted as 11H) located at 3.40 and 3.57 eV for the ZnO/ZnMgO MQWs samples with well widths of 5.6 and 1.2 nm, respectively. The strong anisotropic polarization characteristic has been studied by polarization-dependent PL measurements. For comparison, we also calculated the transition energies of different well thicknesses varying from 1 to 6 nm. The theoretical results match quite well with the experimental values and revealing the suitable conduction band offset Q(c)=0.6. The temperature dependence of PL spectra is being investigated, in the temperature range between 10 and 300 K. (C) 2011 Elsevier B.V. All rights reserved.