Browsing by Author "Hsu, Liang-Ching"

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Deep-Ultraviolet Photodetectors Based on Epitaxial ZnGa(2)O(4 )Thin Films
(2018-09-19)
Tsai, Si-Han
;
Basu, Sarbani
;
Huang, Chiung-Yi
;
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.
Sandwich-Nanostructured n-Cu2O/AuAg/p-Cu2O Photocathode with Highly Positive Onset Potential for Improved Water Reduction
(2019-10-23)
Lin, Yu-Chang
;
Hsu, Liang-Ching
;
Lin, Chia-Yu
;
Chiang, Chao-Lung
;
Chou, Che-Min
An n-Cu2O layer formed a high-quality buried junction with p-Cu2O to increase the photovoltage and thus to shift the turn-on voltage positively. Mott-Schottky measurements confirmed that the improvement benefited from a positive shift in flat-band potential. The obtained extremely positive onset potential, 0.8 V-RHE in n-Cu2O/AuAg/p-Cu2O, is comparable with measurements from water reduction catalysts. The AuAg alloy sandwiched between the homo-junction of n-Cu2O and p-Cu2O improved the photocatalytic performance. This alloy both served as an electron relay and promoted electron-hole pair generation in nearby semiconductors; the charge transfer between n-Cu2O and p-Cu2O in the sandwich structure was measured with X-ray absorption spectra. The proposed sandwich structure can be considered as a new direction for the design of efficient solar-related devices.