Browsing by Author "Lin, Jia-Ching"

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Annealing of defect states in reactive ion etched GaN
(2008-02-01)
Lan, Wen-How
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Huang, Kuo-Chin
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Huang, Kai Feng
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Lin, Jia-Ching
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Cheng, Yi-Cheng
The Al0.11Ga0.89N-based photodiodes fabricated under different annealing ambient after inductively Coupled plasma reactive ion etching process were studied. The dark current and photocurrent with different illuminated wavelengths were characterized. Higher photocurrent for the diode annealing in H-2 ambient can be observed and attributed to the defect-assisted photocurrent. This photocurrent shows a strong annealing ambient dependence and causes the shift of cutoff wavelength in the responsivity spectrum. The Surface state was characterized by the capacitance analysis with Schottky contact. (C) 2007 Elsevier Ltd. All rights reserved.
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
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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.
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
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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
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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.
Photocatalytic study of Zinc Oxide with bismuth doping prepared by spray pyrolysis
(2015-09-01)
Lin, Tzu-Yang
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Hsu, Yu -Ting
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Lan, Wen-How
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Huang, Chien-Jung
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Chen, Lung-Chien
The unintentionally doped and bismuth (Bi) doped zinc oxide (ZnO) films were prepared by spray pyrolysis at 450 degrees C with zinc acetate and bismuth nitrate precursor. The n-type conduction with concentration 6.13 x10(16)cm(-3) can be observed for the unintentionally doped ZnO. With the increasing of bismuth nitrate concentration in precursor, the p-type conduction can be observed. The p-type concentration 4.44x10(17)cm(-3) can be achieved for the film with the Bi/Zn atomic ratio 5% in the precursor. The photoluminescence spectroscopy with HeCd laser light source was studied for films with different Bi doping. The photocatalytic activity for the unintentionally doped and Bi-doped ZnO films was studied through the photodegradation of Congo red under UV light illumination. The effects of different Bi contents on photocatalytic activity are studied and discussed. Results show that appropriate Bi doping in ZnO can increase photocatalytic activity.
Study of E-Mode AlGaN/GaN MIS-HEMT with La-silicate Gate Insulator for Power Applications
(2020-02-01)
Huang, Kuan Ning
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Lin, Yueh-Chin
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Lin, Jia-Ching
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Hsu, Chia Chieh
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Lee, Jin Hwa
An enhancement-mode (E-mode) AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistor (MIS-HEMT) with La2O3/SiO2 gate insulator is investigated for high power application. The La2O3/SiO2 composite oxide formed amorphous La-silicate after post deposition annealing. Good oxide film quality and excellent La-silicate/AlGaN interface properties were achieved as evidenced by the capacitance-voltage (C-V) curves and hysteresis effect of the La-silicate on AlGaN/GaN metal-oxide-semiconductor capacitors. As a result, the E-mode AlGaN/GaN MIS-HEMT with La-silicate gate insulator shows good threshold voltage (V-th) stability and demonstrated only slightly increase in the dynamic on-resistance (R-on) after high drain bias stress test. The device also exhibits high current density of 752 mA/mm, high maximum transconductance of 210 mS/mm, low subthreshold swing of 104 mV/decade, and I-ON/I-OFF = 10(7) when tested at V-DS = 10 V. Furthermore, low on-resistance of 7.6 omega mm, high breakdown voltage of 670 V, and excellent delay time of 4.2 ps were achieved, demonstrating the La-silicate MIS-HEMTs have the potential to be used for power electronic applications.
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
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Huang, Kai-Feng
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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.