Browsing by Author "Hsu, Yu-Ting"

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Conductivity study of nitrogen-doped calcium zinc oxide prepared by spray pyrolysis
(2016-01-15)
Hsu, Yu-Ting
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Lan, Wen-How
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Huang, Kai-Feng
;
Lin, Jia-Ching
;
Chang, Kuo-Jen
In this study, the spray pyrolysis method was used to prepare unintentionally doped and nitrogen-doped calcium zinc oxide films by using zinc acetate, calcium nitrate precursor, and ammonium acetate precursor. Morphological and structural analyses were conducted using scanning electron microscopy and X-ray diffraction. The results indicated that film grain size decreased as the nitrogen doping was increased. Both calcium oxide and zinc oxide structures were identified in the unintentionally doped calcium zinc oxide. When nitrogen doping was introduced, the film mainly exhibited a zinc oxide structure with preferred (002) and (101) orientations. The concentration and mobility were investigated using a Hall measurement system. P-type films with a mobility and concentration of 10.6 cm(2) V-1 s(-1) and 2.8 x 10(17) cm(-3), respectively, were obtained. Moreover, according to a temperature-dependent conductivity analysis, an acceptor state with activation energy 0.266 eV dominated the p-type conduction for the unintentionally doped calcium zinc oxide. By contrast, a grain boundary with a barrier height of 0.274-0.292 eV dominated the hole conduction for the nitrogen-doped calcium zinc oxide films. (C) 2015 Elsevier B.V. All rights reserved.
Effects of Doping Ratio and Thermal Annealing on Structural and Electrical Properties of Boron-Doped ZnO Thin Films by Spray Pyrolysis
(2013-06-01)
Yu, Cheng-Chang
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Hsu, Yu-Ting
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Lee, Shao-Yi
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Lan, Wen-How
;
Kuo, Hsin-Hui
Boron-doped zinc oxide (BZO) thin films have been fabricated by spray pyrolysis on a glass substrate. The morphology and electrical properties of the thin films were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were performed. It was found that [B]/[Zn] ratio altered both the microstructure and concentration of the BZO thin films. The film grain size was reduced by increasing the [B]/[Zn] ratio. The highest Hall mobility was 3.65 cm(2)V(-1)s(-1) for the undoped ZnO thin film, and the highest carrier concentration of 1.0 x 10(19) cm(-3) was achieved for the as-deposited BZO thin film with [B]/[Zn] = 1.5 at. %. Conductivity was determined at different measurement temperatures and shallow donors provided the dominate conduction mechanism for the as-deposited BZO thin films. After 600 degrees C annealing, shallow level reduction and donors with a high activation energy of 129 +/- 6 meV in the BZO thin films were characterized, and the shallow donors that dominate the carrier concentration for the as-deposited spray-pyrolized BZO thin film were eliminated. (C) 2013 The Japan Society of Applied Physics
Effects of UV illumination on oxygen detection for ZnO film prepared by thermally oxidized Zn on sapphire substrate
(2014)
Yu, Cheng-Chang
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Hsu, Yu-Ting
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Lan, Wen-How
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Shih, Ming-Chang
;
Hong, Jin-Hua
The ZnO thin film prepared after the 600 degrees C oxidation of thermally-evaporated Zn thin film on sapphire substrate was studied. A nano structured surface morphology was observed by scanning electron microscope. With following Ti/Au metallization, the metal-semiconductor-metal (MSM) device was formed. With ultra violate (UV) light illumination come from the mercury lamp with a short pass filter, the device resistance variation under oxygen atmosphere was investigated. The reduction of detection response time and recovery time for this device with UV light illumination were observed also. After discussion based on the grain boundary connected model, the observed resistance variation controlled by the nano texture was realized. The UV light illumination technology shows an effective method to enhance the gas detection response time for this ZnO MSM gas sensor. Keywords: ZnO, MSM,
High Electron Mobility AlGaN/AlN/GaN HEMT Structure With a Nano-scale AlN Interlayer
(2012-01-01)
Huang, Shih-Chun
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Chen, Wen-Ray
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Hsu, Yu-Ting
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Lin, Jia-Ching
;
Chang, Kuo-Jen
Epitaxies of AlGaN/AlN/GaN high electron mobility transistor (HEMT) structures with different thickness of nano-scale AlN interlayers have been realized by metalorganic chemical vapor deposition (MOCVD) technology. After epitaxy, high resolution X-ray diffraction (HRXRD), temperature-dependent Hall Effect and atomic force microscopy (AFM) measurements were used to characterize the properties of these samples. First, it was found that the Al composition of AlGaN layer increases from 21.6 to 34.2% with increasing the thickness of AlN interlayer from 0 to 5 nm under the same AlGaN growth conditions. This result may due to the influences of compressive stress and Al incorporation induced by the AlN interlayer. Then, we also found that the room-temperature (RT) electron mobility stays higher than 1500 cm(2)/Vs in the samples within AlN interlayer thickness range of 1.5 nm, on the other hand, the low-temperature (80K) electron mobility drops dramatically from 8180 to 5720 cm(2)/Vs in the samples with AlN interlayer thickness increasing from 1 to 1.5 nm. Furthermore, it was found that the two-dimensional electron gas (2DEG) density increases from 1.15x10(13) to 1.58x10(13) cm(-2) beyond the AlN interlayer thickness of 1 nm. It was also found that the temperature-independent 2DEG densities are observed in the samples with AlN interlayer thickness of 0.5 and 1 nm. The degenerated characteristics of the samples with AlN thickness thicker than 1.5 nm show the degraded crystalline quality which matched the observation of surface defects and small cracks formations from their AFM images. Finally, the 2DEG mobilities of the proposed structures can be achieved as high as 1705 and 8180 cm(2)/Vs at RT and 80K, respectively.
Improved Output Power of Nitride-Based Light-Emitting Diodes With Convex-Patterned Sapphire Substrates
(2012-10-01)
Hsu, Yu-Ting
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Yu, Cheng-Chang
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Huang, Kai-Feng
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Lan, Wen-How
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Huang, Jing-En
Nitride-based light-emitting diodes (LEDs) grown on different convex-patterned sapphire substrates are proposed and fabricated. The electrical and optical properties of these LEDs are discussed in detail. It is found that the LED with a ball-shape patterned sapphire substrate has the best crystalline quality and I-V characteristic. On the other hand, on reducing total internal reflection, the LED with hexagonal-shape patterned sapphire substrate (HPSS) has the best performance on output power and external quantum efficiency. In comparison to the LED without patterned substrate, the LED with HPSS has 175% and 165% enhancement on output power and external quantum efficiency, respectively.
Investigation of the (Cu, Ga) InSe2 thin film with different pairs of CuGa/In sputtered layers
(2012)
Hsu, Yu-Ting
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Huang, Kai-Feng
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Tsai, Shang-I
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Lan, Wen-How
;
Yueh, Ming
Thin film samples of (Cu,Ga) InSe2 (CIGS) were prepared by DC magnetron sputtering and the selenisation process onto soda lime glass substrates. All samples had the same deposition conditions, and the optimal sputtering thickness of samples with one CuGa/In pair and two CuGa/In pairs are also the same. After sample deposition, X-ray diffraction (XRD), scanning electron microscope (SEM) and Hall effect measurements were used to characterize the properties of these samples. From XRD measurement results, excepting an extra small CuSe peak existing in the samples with two CuGa/In pairs, the XRD peaks of all samples are perfectly matched with the phase diagram of CuGa0.3In0.7Se2 material. It was also found that the grain sizes of the samples with one CuGa/In pair are larger than those with two CuGa/In pairs from SEM images. All these observations on samples with two CuGa/In pairs can be attributed to the fact that the less In incorporation in CIGS films, which it has been proven that the sample with low In-to-CuGa ratio has stronger CuSe peak from XRD result. Furthermore, the p-type carrier characteristics can be observed for all samples from Hall measurement results. The carrier mobility and concentration of the samples with one CuGa/In pair can be achieved as high as 15.28 cm(2)/Vs and as low as 1.50x10(16) cm(-3), respectively, while the carrier mobility and concentration of the ones with two CuGa/In pairs can be achieved as 6.4 cm(2)/Vs and 6.27x10(17) cm(-3), respectively. The results of superior electrical properties of samples with one CuGa/In pair agree well with the observations form XRD and SEM results. In the final, the optimal value of In-to-CuGa ratio during CuGa/In layers deposition in this study is 0.625.
On the Nitrogen Doping in Erbium and Nitrogen Codoped Magnesium Zinc Oxide Diode by Spray Pyrolysis
(2020-01-01)
Chen, Chun-An
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Hsu, Yu-Ting
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Lan, Wen-How
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Huang, Kai-Feng
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Chang, Kuo-Jen
Diodes with an erbium and nitrogen codoped magnesium zinc oxide (MgZnO:Er,N) active layer were fabricated by spray pyrolysis on Si substrate with aqueous solutions including magnesium nitrate, zinc acetate, erbium acetate, ammonium acetate, and indium nitrate precursors. Diodes with different nitrogen content in their precursor were prepared and their properties were investigated. With scanning electron microscopy, film surface with mixed hexagonal flakes and tiny blocks was characterized for all samples. Certain morphologies varied for samples with different N contents. In the photoluminescence analyses, the intensity of the oxygen-related defects peak increased with the increasing of nitrogen content. The diodes were fabricated with an Au and In deposition on the top and backside. The diode current-voltage as well as capacitance-voltage characteristics were examined. An ununiformed n-type concentration distribution with high concentration near the interface in the MgZnO:Er,N layer was characterized for all samples. Diodes with high nitrogen content exhibit reduced breakdown voltage and higher interface concentration characteristics. Under reversed bias conditions with an injection current of 50 mA, a light spectrum with two distinct green emissions around wavelengths 532 and 553 nm was observed. A small spectrum variation was characterized for diodes prepared from different nitrogen content. The diode luminescence characteristics were examined and the diode prepared from N/Zn=1 in the precursor showed an optimal injection current-to-luminescence property. The current and luminescence properties of the diode were characterized and discussed.
Thickness Study of Er-Doped Magnesium Zinc Oxide Diode by Spray Pyrolysis
(2018-12-01)
Hsu, Yu-Ting
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Lee, Che-Chi
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Lan, Wen-How
;
Huang, Kai-Feng
;
Chang, Kuo-Jen
Erbium-doped magnesium zinc oxides were prepared through spray pyrolysis deposition at 450 degrees C with an aqueous solution containing magnesium nitrate, zinc acetate, erbium acetate, and indium nitrate precursors. Diodes with different erbium-doped magnesium zinc oxide thicknesses were fabricated. The effect of erbium-doped magnesium zinc oxide was investigated. The crystalline structure and surface morphology were analyzed using X-ray diffraction and scanning electron microscopy. The films exhibited a zinc oxide structure, with (002), (101), and (102) planes and tiny rods in a mixed hexagonal flakes surface morphology. With the photoluminescence analyses, defect states were identified. The diodes were fabricated via a metallization process in which the top contact was Au and the bottom contact was In. The current-voltage characteristics of these diodes were characterized. The structure resistance increased with the increase in erbium-doped magnesium zinc oxide thickness. With a reverse bias in excess of 8 V, the light spectrum, with two distinct green light emissions at wavelengths of 532 nm and 553 nm, was observed. The light intensity that resulted when using a different operation current of the diodes was investigated. The diode with an erbium-doped magnesium zinc oxide thickness of 230 nm shows high light intensity with an operational current of 80 mA. The emission spectrum with different injection currents for the diodes was characterized and the mechanism is discussed.
UV Enhanced Oxygen Response Resistance Ratio of ZnO Prepared by Thermally Oxidized Zn on Sapphire Substrate
(2013)
Yu, Cheng-Chang
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Hsu, Yu-Ting
;
Lan, Wen-How
;
Shih, Ming-Chang
;
Hong, Jin-Hua
ZnO thin film was fabricated by thermally oxidized Zn at 600 degrees C for 1 h. A surface containing nanostructured dumbbell and lines was observed by scanning electron microscope (SEM). The ZnO resistor device was formed after the following Ti/Aumetallization. The device resistance was characterized at different oxygen pressure environment in the dark and under ultraviolet (UV) light illumination coming from the mercury lamp with a short pass filter. The resistance increases with the increase of oxygen pressure. The resistance decreases and response increases with the increase of light intensity. Models considering the barrier height variation caused by the adsorbed oxygen related species were used to explain these results. The UV light illumination technology shows an effective method to enhance the detection response for this ZnO resistor oxygen sensor.