Browsing by Author "Huang, Chiung-Yi"

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Deep-Ultraviolet Photodetectors Based on Epitaxial ZnGa(2)O(4 )Thin Films
(2018-09-19)
Tsai, Si-Han
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Basu, Sarbani
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Huang, Chiung-Yi
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Hsu, Liang-Ching
;
Lin, Yan-Gu
A single-crystalline( )ZnGn(2)O(4) ( )epilayer was successfully grown on c-plane (0001) sapphire substrate by metal-organic chemical vapor deposition. This epilayer was used as a ternary oxide semiconductor for application in high-performance metal-semiconductor-metal photoconductive deep-ultraviolet (DUV) photodetectors (PDs). At a bias of 5V, the annealed ZnGn(2)O(4) PDs showed better performance with a considerably low dark current of 1 pA, a responsivity of 86.3 A/W, cut-off wavelength of 280 nm, and a high DUV-to-visible discrimination ratio of approximately 10(7) upon exposure to 230 nm DUV illumination than that of as-grown ZnGn(2)O(4 )PDs. The as-grown PDs presented a dark current of 0.5 mA, a responsivity of 2782 A/W at 230 nm, and a photo-to-dark current contrast ratio of approximately one order. The rise time of annealed PDs was 0.5 s, and the relatively quick decay time was 0.7 s. The present results demonstrate that annealing process can reduce the oxygen vacancy defects and be potentially applied in ZnGn(2)O(4) film-based DUV PD devices, which have been rarely reported in previous studies.
Deep-ultraviolet Schottky photodetectors with high deep-ultraviolet/visible rejection based on a ZnGa2O4 thin film
(2019-12-01)
Tsai, Si-Han
;
Shen, Yuan-Chu
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Huang, Chiung-Yi
;
Horng, Ray-Hua
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電子工程學系及電子研究所
A single-crystalline ZnGa2O4 epilayer was successfully grown on a c-plane (0001) sapphire substrate through metalorganic chemical vapor deposition. A metal-semiconductor-metal Schottky deep-ultraviolet (DUV) photodetector based on a ZnGa2O4 thin film was fabricated through a simple process of E-gun evaporation and thermal annealing. At a bias of 10 V, the ZnGa2O4 photodetectors exhibited excellent performance characteristics such as an extremely low dark current (0.86 pA), a responsivity of 0.46 A/W under 230-nm DUV, a high photo/dark current ratio (up to 4.68x10(4)), a sharp cutoff wavelength of approximately 270 nm, and short rise and fall times of 0.96 and 0.34 s. The photogenerated holes trapped in the Schottky barrier and the shrinking of the depletion region under DUV illumination enabled high DUV/visible rejection ratio (3-4 orders with a 20-V bias). Therefore, the Fowler-Nordheim field tunneling emission functioned as the main electron transport mechanism under DUV illumination and improved the photoelectric characteristics of the epilayer.
Epitaxial Growth of ZnGa2O4: A New, Deep Ultraviolet Semiconductor Candidate
(2017-11-01)
Huang, Ray-Hua
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Huang, Chiung-Yi
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Ou, Sin-Liang
;
Juang, Tzu-Kuang
;
Liu, Po-Liang
ZnGaO films were grown on c-plane sapphire substrates by metal organic chemical vapor deposition using diethylzinc (DEZn), triethylgallium (TEGa), and oxygen. The flow rate of DEZn was 10-60 sccm, and those of TEGa and oxygen were held constant. The ZnGaO film prepared at a DEZn flow rate of 10 sccm adopted a ((2) over bar 01)-oriented single-crystalline beta-Ga2O3 phase, whereas those prepared at 30-60 sccm exhibited a (111)-oriented single-crystalline ZnGa2O4 phase. On the basis of Hall measurements, ZnGaO films (10 sccm DEZn) possessed very poor electrical properties, which were similar to those of beta-Ga2O3. On the other hand, the carrier concentration in ZnGaO films increased from 1.94 X 10(14) to 6.72 X 10(16) cm(-3), and the resistivity decreased from 5730 to 67.9 Omega-cm when increasing the DEZn flow rate from 30 to 60 sccm. According to compositional analyses, the improved electrical properties of ZnGaO films upon increasing DEZn flow rate from 30 to 40 sccm are due to the increasing Zn content, and the enhancement from 50 to 60 sccm could be due to increased C content. Cathodoluminescence results also confirm the ZnGa2O4 structure for ZnGaO films prepared at DEZn flow rates of 30-60 sccm and reveal their use for ultraviolet applications.
Evolution of the local structure and crystal phase for thin ZnGaO films grown by metal organic chemical vapor deposition
(2019-08-15)
Lin, Xiwen
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Chen, Daihua
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Niu, Wenlong
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Huang, Chiung-Yi
;
Horng, Ray Hua
A systematic investigation is reported to comprehend the atomic and crystal structure of several thin ZnGaO films grown by metal organic chemical vapor deposition method using different flow rates of diethylzinc (DEZn) while keeping triethylgallium and oxygen flow rates constant. The x-ray absorption fine structure analysis has indicated that the local structure of Ga absorbing atom is close to that of beta-Ga2O3 at a lower DEZn flow rate of 30 sccm and transforming to ZnGa2O4 structure at higher 60 sccm. There is a certain proportion of Ga ions that occupies the tetrahedral sites. The ratios of tetrahedral and octahedral Ga species (Ga(t)/Ga(o)) are found to be within 5.5-8.8%. The x-ray diffraction patterns showed the crystal structure of ZnGaO films gradually evolving from monoclinic to cubic phase with an increase of DEZn flow rates from 30 sccm to 60 sccm. One film prepared at 40 sccm displays the best crystalline quality and the other grown at 50 sccm exhibits excellent smooth surface having the lowest root mean square value with a roughness of 0.42 nm. The correlation between atomic and crystal structure and the growth is helpful to understand the formation of single-crystalline ZnGa2O4 and its physical mechanism.
NO gas sensor based on ZnGa2O4 epilayer grown by metalorganic chemical vapor deposition
(2019-05-16)
Wu, Min-Ru
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Li, Wei-Zhong
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Tung, Chun-Yi
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Huang, Chiung-Yi
;
Chiang, Yi-Hung
A gas sensor based on a ZnGa2O4(ZGO) thin film grown by metalorganic chemical vapor deposition operated under the different temperature from 25 degrees C to 300 degrees C is investigated in this study. This sensor shows great sensing properties at 300 degrees C. The sensitivity of this sensor is 22.21 as exposed to 6.25 ppm of NO and its response time is 57 s. Besides that, the sensitivities are 1.18, 1.27, 1.06, and 1.00 when exposed to NO2(500 ppb), SO2 (125 ppm), CO (125 ppm), and CO2 (1500 ppm), respectively. These results imply that the ZGO gas sensor not only has high sensitivity, but also has great selectivity for NO gas. Moreover, the obtained results suggest that ZGO sensors are suitable for the internet of things(IOT) applications.
Thickness Effect on Operational Modes of ZnGa2O4 MOSFETs
(2018-01-01)
Cheng, Li-Chung
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Huang, Chiung-Yi
;
Horng, Ray-Hua
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The device mechanism from depletion to enhancement mode for ZnGa2O4 metal-oxide semiconductor field effect transistors (MOSFETs) grown on the sapphire substrate by metalorganic chemical-vapor deposition was studied. It was found that the thickness of the ZnGa2O4 thin-film would affect the operational mode of the MOSFETs. Under the low-voltage operation (V-DS = 0.5 V), the transistors exhibited a high on/off ratio from 10(7) to 10(4), low subthreshold swing from 150 to 330 mV/dec, high field-effect mobility from 4.2 to 0.054 cm(2)/V-s and threshold voltages from - 17.8 to 4.1 V (using constant current = 1 nA). These electrical properties all depend on the thickness of the ZnGa2O4 thin-film transistors. Finally, the e-mode ZnGa2O4 thin-film transistor with off-state breakdown voltage over 400 V is fabricated.