Publications (268)405.05 Total impact
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Article: High-Sensitivity Nitride-Based Ultraviolet Photosensors with a Low-Temperature AlGaN Interlayer
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ABSTRACT: Nitride-based ultraviolet (UV) photosensors with a low-temperature (LT) AlGaN interlayer were fabricated and characterized. Material analysis results showed that dark pits corresponding to threading dislocation (TD) terminations were almost invisible after inserting the LT AlGaN interlayer. It was also found that we could significantly suppress the dark leakage current by using the LT AlGaN interlayer owing to TD annihilation and demultiplication processes. For photosensors with the LT AlGaN interlayer, the responsivity at 360nm and UV-to-visible rejection ratio were found to be 0.12A/W and 2.45×103, respectively, under 5V applied bias.Journal of Electronic Materials 04/2012; 39(1):29-33. · 1.47 Impact Factor -
Article: Enhancement of Light Output Power of GaN-Based Light-Emitting Diodes by a Reflective Current Blocking Layer
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ABSTRACT: In this study, a GaN-based light-emitting diode (LED) with a distributed Bragg reflector (DBR) current blocking layer (CBL) beneath the p-pad electrode is demonstrated. A high reflectivity DBR structure is composed of five periods SiO<sub>2</sub> and TiO<sub>2</sub> layers. At a driving current of 20 mA, the light output power of the LEDs with DBR CBL was 16.8% and 11.3% higher than the LEDs without and with SiO<sub>2</sub> CBL. The improvement is contributed to the DBR CBL can deflect the current away from the p-electrode pad and also prevent the light absorption by the opaque metal electrode. It was found that LEDs with DBR CBL shows better current spreading and broader far-field pattern.IEEE Photonics Technology Letters 08/2011; · 2.19 Impact Factor -
Article: Localized Surface Plasmon-Enhanced Nitride-Based Light-Emitting Diode With Ag Nanotriangle Array by Nanosphere Lithography
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ABSTRACT: We describe a method to enhance the light output power of nitride-based light-emitting diodes (LEDs) through the coupling of multiple quantum wells (MQWs) with localized surface plasmon (LSP). The LSP was generated on an Ag nanotriangle array (NTA) on a 40-nm-thick p-type GaN layer beneath the p-pad of the LED, which was partially etched by inductively coupled plasma system. The Ag NTA was fabricated by nanosphere lithography. The resonant frequency of a generated LSP can be precisely controlled by changing the size of the polystyrene nanosphere and the Ag deposition thickness. Under the optimum conditions, the light output power of LED with an Ag NTA was 15.4% higher than LED without an Ag NTA at an inject current of 20 mA. The improvement in light output power can be attributed to the coupling effect between MQW and LSP.IEEE Photonics Technology Letters 08/2010; · 2.19 Impact Factor -
Article: AlGaN/GaN high electron mobility transistors based on InGaN/GaN multiquantum-well structures
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ABSTRACT: We report an AlGaN/GaN high electron mobility transistors (HEMTs) based on InGaN/GaN multiquantum-well (MQW) structure. When InGaN/GaN MQW structure was inserted, InGaN layer has an opposite piezoelectric polarization field compared to AlGaN, which results in a very sharp rise of the conduction band. The raised potential barrier can help to improve carrier confinement and obtain a larger main peak transconductance of 111 mS/mm and satellite peak transconductance of 24 mS/mm, corresponding to AlGaN/GaN heterojunction and InGaN layer. MQW-based metal-oxide-semiconductor-HEMT was also fabricated and significantly reduced the leakage current and increased transconductance as a result of passivation by Ta2O5 gate oxide.Applied Physics Letters 05/2010; 96(21):212105-212105-3. · 3.84 Impact Factor -
Article: III-Nitride Schottky Rectifiers With an AlGaN/GaN/AlGaN/GaN Quadruple Layer and Their Applications to UV Detection
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ABSTRACT: III-nitride Schottky rectifiers (SRs) with (i.e., SR_A) and without (i.e., SR_B) the AlGaN/GaN/AlGaN/GaN quadruple layer were both fabricated. It was found that we could achieve a lower leakage current from SR_A. Under reverse bias, it was found that SR_A showed a more than five orders magnitude smaller dark current than that in SR_B. It was also found that lower on-state resistance was due to the larger Schottky barrier height and larger breakdown voltage was due to reduced defect densities in SR_A. The SRs with a quadruple layer was suitable for applications to low noise or/and ultraviolet (UV) detection as well.IEEE Sensors Journal 05/2010; · 1.52 Impact Factor -
Article: Effect of period of the electron emitter MQW structure on the improvement of characteristics in nitride‐based LEDs
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ABSTRACT: The effect of period of electron emitter multiple-quantum well (EE-MQW) structure on the structural, electrical, and optical characteristics of nitride-based light-emitting diodes (LEDs) were investigated. From the lattice constant results of InGaN/GaN multiple-quantum well (MQW) by the high resolution X-ray diffraction, the compressive strain of InGaN/GaN MQW could be released gradually when the period of EE-MQW structure increases. Therefore, the leakage current reduces and the ESD endurance ability enhances with increasing period of EE-MQW structure. On the other hand, the electron injection efficiency will also be improved by inserting EE-MQW structure. When the period of EE-MQW structure increases, the forward voltage and series resistance both decrease. Due to the improved electron injection efficiency and crystalline quality, the luminance intensity increases with increasing period of EE-MQW structure. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)physica status solidi (c) 04/2010; 7(7‐8):2162 - 2164. -
Conference Proceeding: An in-depth study on the fabrication of 1055–1064 nm multi-quantum-well and super-lattice laser diodes
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ABSTRACT: In this paper the InGaAs/GaAs multi-quantum-well as well as the AlGaAs/GaAs and the GaAsP/GaAs super-lattice material systems have been employed to develop 1055-1064 nm quantum-well laser diodes, including epitaxial growth and device fabrication technologies. The semiconductor-type seed laser can be used in the pulsed optical-fiber system. Extensive research efforts have been made to generate blue and green light directly from semiconductor laser diodes because of their various advantages such as low noise, high-frequency modulation capability, wavelength tunability, compactness, and easy integration. Because the low-cost GaAs substrate was adopted, it is expected that the manufacturing expense of the optical communication network will be reduced as well as the lasing performance will be excellent, and it is very helpful for the future global optical-fiber platform implementation.Microsystems, Packaging, Assembly and Circuits Technology Conference, 2009. IMPACT 2009. 4th International; 11/2009 -
Article: Low Transparency Current Density and Low Internal Loss of 1060-nm InGaAs Laser With GaAsP–GaAs Superlattices as Strain-Compensated Layer
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ABSTRACT: In this letter, the strained In<sub>0.22</sub>Ga<sub>0.78</sub>As-GaAs single quantum-well lasers grown by metal-organic vapor phase epitaxy were studied. The lasing wavelength of the fabricated InGaAs laser was 1056 nm, whereas the internal loss (alpha<sub>i</sub>) and the transparency current density (J<sub>tr</sub>) were 1.78 cm<sup>-1</sup> and 40.2 A/cm<sup>2</sup>, respectively. By using the GaAsP-GaAs superlattices as strain-compensated layer, the lasing wavelength was 1052 nm, and the alpha<sub>i</sub> and J<sub>tr</sub> could be reduced to 0.63 cm<sup>-1</sup> and 39.1 A/cm<sup>2</sup>, respectively. To the best of our knowledge, the J<sub>tr</sub> was the lowest among the reported InGaAs lasers around 1060 nm.IEEE Photonics Technology Letters 11/2009; · 2.19 Impact Factor -
Article: Ultraviolet ZnO nanorod photosensors.
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ABSTRACT: This study fabricates and characterizes ultraviolet (UV) photosensors with ZnO nanorods (NRs). The NR arrays were selectively grown in the gap between interdigitated (IDT) electrodes of devices using hydrothermal solution processes and a lithography-based technique. Compared with a conventional ZnO photosensor without NRs, the proposed UV NR photosensors have much higher photoresponse in the UV region. Additionally, the photoconductive gain of an NR photosensor increased as UV illumination time increased; it varied at 34.45-5.32 x 10(2) under illumination by 18.28 mW/cm(2) optical power. Consequently, the substantial photoconductive gain can be attributed to high surface-to-volume ratio of ZnO NRs. The high density of hole-trap states on NR surfaces lead to a persistent photoconductivity (PPC) state, promoting the transport of carriers through devices.Langmuir 11/2009; 26(1):603-6. · 4.19 Impact Factor -
Article: AlGaN/GaN two-dimensional electron gas Schottky barrier photodiodes with multiple MgxNy/GaN layers
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ABSTRACT: In this study, AlGaN/GaN two-dimensional electron gas (2DEG) heterostructures were grown by metal organic chemical vapor deposition (MOCVD). It was found that we could reduce reverse leakage current and provide high-voltage operation by introducing multiple MgxNy/GaN layers into the conventional Schottky barrier photodiodes (SBPD). An atomic force microscopy (AFM) scan image showed that surface pits of TD terminations were hardly observed as the multiple MgxNy/GaN layers were grown before subsequently depositing a high-temperature (HT) AlGaN/GaN epitaxial layer. A larger Schottky barrier height (ΦB) and smaller ideality factor (n) extracted from the current–voltage (I–V) curve for SBPD with multiple MgxNy/GaN layers also suggested that better crystal quality and rectifying properties were achieved. The larger value of ΦB might be explained by the reduction of the TD density and interface state (IS) density.Semiconductor Science and Technology 09/2009; 24(10):105005. · 1.72 Impact Factor -
Article: Temperature dependent surface photovoltage spectroscopy characterization of highly strained InGaAs/GaAs double quantum well structures grown by metal organic vapor phase epitaxy
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ABSTRACT: Highly strained In <sub>x</sub> Ga <sub>1-x</sub> As / GaAs double quantum well (DQW) structures grown by metal organic vapor phase epitaxy with different In compositions are investigated by surface photovoltage spectroscopy (SPS) in the temperature range 20–300 K. A lineshape fit of spectral features in the differential surface photovoltage (SPV) spectra determines the transition energies accurately. A comprehensive analysis of the anomalous phenomena appearing in lower temperature SPV spectra enable us to evaluate directly the band lineup of DQW and to remove the ambiguity in the identification of spectral features. The process of separation of carriers within the QW with possible capture by the interface defect traps plays an important role for phase change in SPV signal in the vicinity of light-hole related feature at low temperature. The results demonstrate the considerable diagnostic values of the SPS technique for characterizing these highly strained DQW structures.Journal of Applied Physics 09/2009; · 2.17 Impact Factor -
Article: Ultraviolet photodetectors based on selectively grown ZnO nanorod arrays
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ABSTRACT: Metal-semiconductor-metal (MSM) ultraviolet (UV) photodetectors with ZnO nanorods (NRs) have been fabricated and characterized in this investigation. The NR arrays were selectively grown on the gap of interdigitated electrodes by chemical solution method through a photolithography process. Compared to a traditional ZnO MSM photodetector with no NRs, the fabricated NR UV photodetector showed much higher photoresponsity. As a result, it can be attributed to high surface-to-volume ratio of ZnO NRs and such a high photoresponse could strongly depend on oxygen adsorption/desorption process in the presence of trap states at the NR surface.Applied Physics Letters 06/2009; · 3.84 Impact Factor -
Article: Effect of the Phase Shift in a Periodic Anode on the Emission Spectra of Top-Emitting Organic Light-Emitting Diodes
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ABSTRACT: Top-emitting organic light-emitting diodes with an Al-Ag cathode and Al +(Ni-Au)<sub>n</sub> anode were proposed and fabricated. The multiple layered anode results in a phase shift at the metal interfaces. It was also found that theoretically calculated peak wavelengths of the intensity spectra agree well with those experimentally measured from the fabricated devices. These results also indicate that the phase shift effect in periodic anode is important for microcavity devices.IEEE Photonics Technology Letters 12/2008; · 2.19 Impact Factor -
Article: GaN Metal–Semiconductor–Metal Photodetectors With SiN/GaN Nucleation Layer
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ABSTRACT: In this paper, GaN metal-semiconductor-metal (MSM) photodetectors with SiN/GaN nucleation layer were proposed and fabricated. Compared with the GaN MSM photodetector with conventional single low-temperature GaN nucleation layer, it was found that we achieved much smaller dark current and much lower bias-dependent photocurrent. We also achieved much lower bias-dependent spectral response and larger ratio of photoresponse at 360-450 nm from the photodetector with SiN/GaN nucleation layer. Furthermore, it was found that we can significantly reduce noise-equivalent power (NEP) and enhance normalized detectivity by using the SiN/GaN nucleation layer.IEEE Sensors Journal 11/2008; · 1.52 Impact Factor -
Article: Degeneration of CMOS Power Cells After Hot-Carrier and Load Mismatch Stresses
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ABSTRACT: In this letter, we investigate the performance degradation of nMOS transistors due to hot-carrier effect and load impedance mismatch. The DC and radio-frequency characteristics, such as drain current, threshold voltage, transconductance, output power, power-added efficiency, etc., are affected under hot-carrier effect. With load impedance mismatch, the transistors experience the reflected power from load and increase the energy of hot carriers. This effect will make DC and power performances degenerate heavily. In this letter, device characteristics were measured at 5.2 GHz.IEEE Electron Device Letters 10/2008; · 2.85 Impact Factor -
Article: Low Dark Current GaN p-i-n Photodetectors With a Low-Temperature AlN Interlayer
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ABSTRACT: GaN p-i-n ultraviolet (UV) photodetectors (PDs) with a low-temperature (LT)-AlN interlayer were proposed and fabricated. It was found that the dark current of such detectors is as small as 28pA even at a high reverse bias of 40 V. Although the high potential barrier at the AlN-GaN interface would slightly reduce the responsivity of PD under low reverse biases, the high UV-to-visible rejection ratio of the PD with an LT-AlN interlayer could be achieved under high reverse biases due to its very low dark current. The rejection ratio of the PD with the LT-AlN interlayer is as large as 735 at the reverse bias of 40 V.IEEE Photonics Technology Letters 08/2008; · 2.19 Impact Factor -
Article: Enhanced Output Power of GaN-Based LEDs With Nano-Patterned Sapphire Substrates
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ABSTRACT: GaN-based light-emitting diodes (LEDs) with an emitting wavelength of 450 nm were grown on nano-patterned sapphire substrates (NPSS) fabricated by nanosphere lithography. The crystalline quality of the epitaxial film could be improved by using the NPSS technique. The output power of LED grown on NPSS was 1.3 and 1.11 times higher than those of LEDs grown on conventional and patterned sapphire substrates at the injection current of 20 mA, respectively. The enhancement in output power could be contributed to the efficiently scattering by NPSS. But some voids formed at the GaN/NPSS interface cause a thermal dissipation problem of NPSS LED operated at high injection current.IEEE Photonics Technology Letters 08/2008; · 2.19 Impact Factor -
Article: Characterization of Mg-Doped AlInN Annealed in Nitrogen and Oxygen Ambients
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ABSTRACT: Mg-doped AlInN grown by metalorganic chemical vapor deposition (MOCVD) was demonstrated using the postgrowth thermal treatment in nitrogen and oxygen ambients. High-resolution x-ray diffraction (HRXRD) measurements showed that the crystalline quality of AlInN depends on the indium content, which is attributed to the effect of the lattice mismatch between AlInN and GaN. Interestingly, the formation of rod-shaped AlInN, which possibly resulted from the oxidation process, was observed after the postgrowth thermal treatment in the oxygen ambient. Furthermore, an InGaN/GaN multiple-quantum-well (MQW) light-emitting diode (LED) with an AlInN cladding layer was also fabricated. We believe that Mg-doped AlInN, nearly lattice matched to GaN, could play an important role for the further development of lattice-matched AlInN/GaN device applications.Journal of Electronic Materials 07/2008; 37(8):1070-1075. · 1.47 Impact Factor -
Conference Proceeding: Thermal management and novel package design of high power light-emitting diodes
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ABSTRACT: Thermal management and package materials in high power light emitting diodes (HPLEDs) are now critical design issues to limit their luminous intensity, reliability, and applications. In this paper electroless and electroplating techniques (EET) were both applied in fabrication of the red, green, and blue HPLEDs (RGB HPLEDs) chips. The HPLEDs with conventional package structures were fixed on the lead frames by adhesives, but the HPLEDs using EET were fixed on copper substrates without any adhesive resin. In our work, the results show that the thermal resistance of HPLED using EET is much less than one of the HPLED using adhesive resin. The maximum luminous intensity of the single chip HPLED using EET is larger than HPLED with resin/MCPCB (metal core printed circuit board) in room temperature.Electronic Components and Technology Conference, 2008. ECTC 2008. 58th; 06/2008 -
Article: Gan p-i-n photodetectors with an LT-GaN interlayer
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ABSTRACT: Nitride-based p-i-n ultraviolet (UV) photodetectors with a low-temperature (LT) GaN interlayer were proposed and fabricated. Compared with a conventional GaN p-i-n photodetector, it was found that both the dark current and ideality factor of the p-i-n photodetector with an LT-GaN interlayer became larger whereas the UV-to-visible rejection ratio became smaller because of the poor crystal quality of the LT-GaN interlayer. However, the responsivity of the GaN p-i-n photodetector with an LT-GaN interlayer was larger than that of the conventional GaN p-i-n photodetector under a high reverse bias because of the carrier multiplication effect and/or internal gain that originated from the defect levels.IET Optoelectronics 05/2008; · 1.03 Impact Factor
Top co-authors
Top Journals
Institutions
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2009
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Kun Shan University
Fengshan, Taiwan, Taiwan
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1979–2009
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National Cheng Kung University
- Department of Electrical Engineering
Tainan, Taiwan, Taiwan
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2008
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Chung Shan Institute of Science and Technology
Taoyuan, Taiwan, Taiwan
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2001–2002
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National Central University
Taoyuan City, Taiwan, Taiwan
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1995
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National Sun Yat-sen University
- Department of Physics
Kaohsiung, Kaohsiung, Taiwan
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1994
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Industrial Technology Research Institute
Hsinchu, Taiwan, Taiwan
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