Browsing by Author "Huang, Huei-Min"

Now showing 1 - 20 of 21

Abnormal polarization switching phenomenon in a-plane Al(x)Ga(1-x)N
(2010-10-11)
Huang, Huei-Min
;
Huang, Hung-Hsun
;
Wu, Yuh-Renn
;
Lu, Tien-Chang
;
光電工程學系
The optical polarization properties of a-plane Al(x)Ga(1-x)N films have been investigated by polarization-dependent photoluminescence (PL). The degree of polarization decreased with increasing the Al composition, and the main optical polarization direction switched from epsilon perpendicular to c to epsilon // c at about x = 0.07 due to the valence band switching, representing that the optical transition energy of epsilon // c is surpassing that of epsilon perpendicular to c. However, with the Al composition larger than x = 0.1, the higher energy optical transitions of epsilon // c exhibited the stronger PL intensity, opposite to the normal situations that higher energy states commonly have weaker PL intensity than the lower energy states. We utilized the 6 x 6 k.p model and the lambertian-like radiation pattern assumption to explain this abnormal optical polarization switching behavior in the a-plane Al(x)Ga(1-x)N layers and obtained good agreement with the experimental results. (C) 2010 Optical Society of America
Abnormal polarization switching phenomenon in a-plane Al(x)Ga(1-x)N
(2011-01-01)
Huang, Huei-Min
;
Huang, Hung-Hsun
;
Wu, Yuh-Renn
;
Lu, Tien-Chang
;
Kuo, Hao-Chung
The a-plane Al(x)Ga(1-x)N layers show abnormal optical polarization switching behavior. This phenomenon can be well characterized by the assumption of the lambertian-like radiation pattern and simulated by utilizing the 6 x 6 k . p model. (C) 2010 Optical Society of America
Abnormal polarization switching phenomenon in a-plane AlxGa1-xN
(2010-10-11)
Huang, Huei-Min
;
Huang, Hung-Hsun
;
Wu, Yuh-Renn
;
Lu, Tien-Chang
;
照明與能源光電研究所
The optical polarization properties of a-plane AlxGa1-xN films have been investigated by polarization-dependent photoluminescence (PL). The degree of polarization decreased with increasing the Al composition, and the main optical polarization direction switched from epsilon perpendicular to c to epsilon // c at about x = 0.07 due to the valence band switching, representing that the optical transition energy of epsilon // c is surpassing that of epsilon perpendicular to c. However, with the Al composition larger than x = 0.1, the higher energy optical transitions of epsilon // c exhibited the stronger PL intensity, opposite to the normal situations that higher energy states commonly have weaker PL intensity than the lower energy states. We utilized the 6 x 6 k.p model and the lambertian-like radiation pattern assumption to explain this abnormal optical polarization switching behavior in the a-plane AlxGa1-xN layers and obtained good agreement with the experimental results. (C) 2010 Optical Society of America
Abnormal polarization switching phenomenon in a-plane AlxGa1-xN
(2011-01-01)
Huang, Huei-Min
;
Huang, Hung-Hsun
;
Wu, Yuh-Renn
;
Lu, Tien-Chang
;
Kuo, Hao-Chung
The a-plane AlxGa1-xN layers show abnormal optical polarization switching behavior. This phenomenon can be well characterized by the assumption of the lambertian-like radiation pattern and simulated by utilizing the 6 x 6 k . p model. (C) 2010 Optical Society of America
Characteristics of Polarized Light Emission in a-Plane GaN-Based Multiple Quantum Wells
(2012-07-01)
Chang, Chiao-Yun
;
Huang, Huei-Min
;
Lai, Chih Ming
;
Lu, Tien-Chang
;
光電工程學系
In this paper, we investigated polarized light emission properties on a series of a-plane GaN/AlGaN multiple quantum wells grown on r-plane sapphire substrates with various well widths by using the polarization-dependent photoluminescence measurement. To clarify reasons of polarization properties in light emission, we applied the 6 x 6 k.p model to simulate the E-K dispersion relationship and wave functions to obtain optical transitions of different polarized emissions. According to our results, the sub-bands of vertical bar Y>-like states are raised toward the top of the valence sub-band level with increasing the well width. And the optical matrix element of y-polarized light emission will dominate the optical transition, leading to the increase of degree of polarization in the thicker well.
Depth-resolved confocal micro-Raman spectroscopy for characterizing GaN-based light emitting diode structures
(2013-11-01)
Chen, Wei-Liang
;
Lee, Yu-Yang
;
Chang, Chiao-Yun
;
Huang, Huei-Min
;
Lu, Tien-Chang
In this work, we demonstrate that depth-resolved confocal micro-Raman spectroscopy can be used to characterize the active layer of GaN-based LEDs. By taking the depth compression effect due to refraction index mismatch into account, the axial profiles of Raman peak intensities from the GaN capping layer toward the sapphire substrate can correctly match the LED structural dimension and allow the identification of unique Raman feature originated from the 0.3 mu m thick active layer of the studied LED. The strain variation in different sample depths can also be quantified by measuring the Raman shift of GaN A(1)(LO) and E-2(high) phonon peaks. The capability of identifying the phonon structure of buried LED active layer and depth-resolving the strain distribution of LED structure makes this technique a potential optical and remote tool for in operando investigation of the electronic and structural properties of nitride-based LEDs. (C) 2013 AIP Publishing LLC.
Enhanced internal quantum efficiency in graphene/InGaN multiple-quantum-well hybrid structures
(2012-08-06)
Huang, Huei-Min
;
Chang, Chiao-Yun
;
Hsu, Yueh-Shan
;
Lu, Tien-Chang
;
Lan, Yu-Pin
The enhanced internal quantum efficiency of InGaN/GaN multiple-quantum-wells (MQWs) structure is demonstrated by paving the graphene layers on the MQWs surface. Compared to the conventional MQWs, the internal quantum efficiency of the graphene/InGaN MQWs hybrid structure exhibits a remarkable 2-fold increase. The high charge carrier density in graphene layer is accounted for the enhanced internal quantum efficiency. Moreover, the negligible photoluminescence emission peak shift with increasing the excitation power as well as the decrease of radiative recombination lifetime are attributed to the reduced quantum-confined Stark effect, which correlates to the screening of the polarization field in the c-plane nitride-based quantum well structure. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4745211]
Exciton Localization Behaviors of Basal Stacking Faults in a-Plane AlGaN Alloys
(2011)
Huang, Huei-Min
;
Wu, Yung-Chi
;
Lu, Tien-Chang
;
光電工程學系
;
Department of Photonics
We study the basal plane stacking faults (BSFs) related optical properties in a-plane AlGaN alloys with different Al composition ranging from 0 to 0.28. The low-temperature photoluminescence (PL) spectra for AlGaN show two dominant peaks attributed to the emission of near band edge and BSFs-bound excitons, respectively. The PL integrated intensity ratio of the BSFs to NBE is found to correlate to the density of BSFs observed by the transmission electron microscopy. Finally, the exciton localization behaviors of BSFs in a-plane AlGaN alloys is observed and discussed in this study. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3561422] All rights reserved.
Growth and Characteristics of a-Plane GaN on ZnO Heterostructure
(2012)
Huang, Huei-Min
;
Kuo, Chin-Chia
;
Chang, Chiao-Yun
;
Lin, Yuan-Ting
;
Lu, Tien-Chang
We report on growth and characteristics of a-plane GaN/ZnO/GaN epitaxial structures, which can be applied to various optoelectronic devices. The unique optical transitions intrinsic to heterovalent interfaces were found and analyzed. Clear carrier localization effect in the GaN/ZnO heterointerface is observed from the S-shaped energy shift with increasing temperature in the temperature-dependent photoluminescence measurement. The carrier localization also results in strong luminescent intensity and dominates the emission spectrum at room temperature. In addition, the acceptor level originated from the Zn out-diffusion from the ZnO layer is observed in the low temperature photoluminescence spectra, and its binding energy is estimated to be about 0.311 eV. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.080203jes] All rights reserved.
Growth and Characteristics of a-Plane GaN on ZnO Heterostructure
(2013)
Huang, Huei-Min
;
Kuo, Chin-Chi
;
Chang, Chiao-Yun
;
Lin, Yuan-Ting
;
Lu, Tien-Chang
High quality factor nonpolar GaN photonic crystal nanocavities
(2013-05-13)
Wu, Tzeng-Tsong
;
Lo, Sheng-Yun
;
Huang, Huei-Min
;
Tsao, Che-Wei
;
Lu, Tien-Chang
High quality factor a-plane nonpolar GaN two-dimensional photonic crystal (PC) nanocavities on r-plane sapphire substrates have been demonstrated. Nonpolar GaN PC nanocavities on a thin membrane structure were realized by using e-beam lithography to define the PC patterns and focused-ion beam milling to fabricate the suspended thin membrane. A dominant resonant mode at 388 nm with a high quality factor of approximately 4300 has been demonstrated at 77K by the micro-photoluminescence system. Moreover, the degree of polarization of the emission from the non-polar GaN PC nanocavity was measured to be 64% along the m crystalline direction. (C) 2013 AIP Publishing LLC.
Investigation of Emission Polarization and Strain in InGaN-GaN Multiple Quantum Wells on Nanorod Epitaxially Lateral Overgrowth Templates
(2011-09-15)
Huang, Huei-Min
;
Lu, Tien-Chang
;
Chang, Chiao-Yun
;
Ling, Shih-Chun
;
Chan, Wei-Wen
Non-polar (a-plane) InGaN-GaN multiple quantum wells (MQWs) on the GaN nanorod epitaxially lateral overgrowth templates with different nanorod height have been fabricated. The average in-plane strain in the InGaN MQWs has been determined from 2.73 x 10(-2) to 2.58 x 10(-2) while the nanorod height in templates increases from 0 to 1.7 mu m. The polarization ratio of the emission from InGaN MQWs varies from 85% to 53% along with the increase of the GaN nanorod height. The reduction of polarization ratio has been attributed to the partial strain relaxation within the epitaxial structures as a result of growth on the GaN nanorod templates and the micro-size air-voids observed in the nanorod templates.
Investigation of emission polarization and strain in InGaN/GaN multiple quantum wells on nanorod epitaxially lateral overgrowth templates
(2012)
Huang, Huei-Min
;
Lu, Tien-Chang
;
Chang, Chiao-Yun
;
Lan, Yu-Pin
;
Ling, Shih-Chun
Non-polar (a-plane) InGaN/GaN multiple quantum wells (MQWs) on the GaN nanorod epitaxially lateral overgrowth templates with different nanorod height have been fabricated. The average in-plane strain in the InGaN MQWs has been determined from 2.73x10(-2) to 2.58x10(-2) while the nanorod height in templates increases from 0 to 1.7 mu m. The polarization ratio of the emission from InGaN MQWs varies from 85 % to 53 % along with the increase of the GaN nanorod height. The reduction of polarization ratio has been attributed to the partial strain relaxation within the epitaxial structures as a result of growth on the GaN nanorod templates and the micro-size air-voids observed in the nanorod templates.
Magnitude-tunable sub-THz shear phonons in a non-polar GaN multiple-quantum-well p-i-n diode
(2012-05-14)
Chen, Chien-Cheng
;
Huang, Huei-Min
;
Lu, Tien-Chang
;
Kuo, Hao-Chung
;
Sun, Chi-Kuang
Coherent transverse acoustic phonons are optically generated and detected through the piezoelectric coupling between the build-in electric fields and shear strains of a non-polar GaN multiple quantum wells embedded in a p-n junction. By optical transient transmission change measurement, the phonon frequency is observed to be 0.4 THz which corresponds to a wavelength of 12.5 nm, the periodicity of the multiple quantum wells, and the estimated phonon velocity corresponds to the transverse acoustic phonon velocity in GaN. Moreover, we can magnify the driving amplitude of the generated shear phonons by increasing the reverse bias of the p-i-n diode. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4718524]
NONPOLAR GAN TWO DIMENSIONAL PHOTONIC CRYSTAL H2 HIGH QUALITY FACTOR NANOCAVITIES
(2013-01-01)
Lu, Tien-Chang
;
Wu, Tzeng-Tsong
;
Lo, Sheng-Yun
;
Tsao, Che-Wei
;
Huang, Huei-Min
Nonpolar GaN two-dimensional photonic crystal (PC) H2 nanocavities have been realized and investigated. One dominated resonant mode was demonstrated at 388 nm with quality factor of approximately 4300 at 77K. Moreover, the degree of polarization of the emission from the non-polar GaN PC nanocavity was measured to be 64% along the m crystalline direction.
Optical Properties of A-Plane InGaN/GaN Multiple Quantum Wells Grown on Nanorod Lateral Overgrowth Templates
(2011-08-01)
Huang, Huei-Min
;
Ling, Shih-Chun
;
Chan, Wei-Wen
;
Lu, Tien-Chang
;
Kuo, Hao-Chung
A-plane InGaN/GaN multiple-quantum wells (MQWs) were grown on a series of nanorod epitaxial lateral overgrowth (NRELOG) templates with varied nanorod depth. Optical properties of these samples were investigated by excitation power and temperature-dependent photoluminescence (PL). Due to the absence of quantum-confined Stark effect, the negligible PL emission peak shift and nearly identical power index for all samples were observed. In contrast to the as-grown MQWs, the thermal activation energy and internal quantum efficiency of NRELOG MQWs exhibit 1.6-fold and 4-fold increases, respectively, which are attributed to the improvement of crystal quality by NRELOG. Furthermore, the Shockley-Read-Hall nonradiative coefficient, determined from the fits of power-dependent PL quantum efficiency, is also apparently reduced while MQWs are grown on NRELOG GaN template. The results show the feasibility to fabricate high radiative efficiency a-plane devices via NRELOG.
Passivation of yellow luminescence defects in GaN film by annealing and CF(4) plasma treatment
(2011-07-01)
Chen, Hsiang
;
Kao, Chyuan-Haur
;
Chen, Yi-Chen
;
Lo, Hong-Kai
;
Yeh, Yih-Min
In this study, we demonstrated that yellow luminescence (YL) defects can be mitigated with proper annealing or CF(4) plasma treatment. Multiple material analyses, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and surface roughness measurements were performed to investigate improvements in GaN film material properties caused by annealing and CF(4) plasma treatment. Filling vacancies during the annealing process and incorporating fluorine atoms to bond with dangling bonds during the plasma treatment process may lessen YL defects and decrease YL luminescence.
Passivation of yellow luminescence defects in GaN film by annealing and CF4 plasma treatment
(2011-07-01)
Chen, Hsiang
;
Kao, Chyuan-Haur
;
Chen, Yi-Chen
;
Lo, Hong-Kai
;
Yeh, Yih-Min
In this study, we demonstrated that yellow luminescence (YL) defects can be mitigated with proper annealing or CF4 plasma treatment. Multiple material analyses, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and surface roughness measurements were performed to investigate improvements in GaN film material properties caused by annealing and CF4 plasma treatment. Filling vacancies during the annealing process and incorporating fluorine atoms to bond with dangling bonds during the plasma treatment process may lessen YL defects and decrease YL luminescence.
Study of Nonpolar GaN/ZnO Heterostructures Grown by Molecular Beam Epitaxy
(2013-07-01)
Chang, Chiao-Yun
;
Huang, Huei-Min
;
Lan, Yu-Pin
;
Lu, Tien-Chang
;
Tu, Li-Wei
The growth mechanism and characteristics of the nonpolar GaN/ZnO heterostructure grown on the r-plane sapphire substrate by using molecular beam epitaxy were studied. The crystal interaction between GaN and ZnO epitaxial layers was clarified by using transmission electron microscopy and X-ray diffraction. A new epitaxial relationship of ZnGa2O4 (220)//GaN (10 (13) over bar) in the normal surface direction was obtained in the GaN/ZnO heterostructure. It was believed that the formation of ZnGa2O4 (220) was due to the recrystallizadon of the ZnO layer with Ga atoms, which in turn resulted in the formation of semipolar-oriented GaN. In addition, the main optical transition in the GaN/ZnO heterostructure was attributed to the existence of the interface states and new ZnO:(Ga,N) alloys.
Study of Nonpolar GaN/ZnO Heterostructures Grown by Molecular Beam Epitaxy
(2013-07-01)
Chang, Chiao-Yun
;
Huang, Huei-Min
;
Lan, Yu-Pin
;
Lu, Tien-Chang
;
Tu, Li-Wei
The growth mechanism and characteristics of the nonpolar GaN/ZnO heterostructure grown on the r-plane sapphire substrate by using molecular beam epitaxy were studied. The crystal interaction between GaN and ZnO epitaxial layers was clarified by using transmission electron microscopy and X-ray diffraction. A new epitaxial relationship of ZnGa2O4 (220)//GaN (10 (13) over bar) in the normal surface direction was obtained in the GaN/ZnO heterostructure. It was believed that the formation of ZnGa2O4 (220) was due to the recrystallizadon of the ZnO layer with Ga atoms, which in turn resulted in the formation of semipolar-oriented GaN. In addition, the main optical transition in the GaN/ZnO heterostructure was attributed to the existence of the interface states and new ZnO:(Ga,N) alloys.