Browsing by Author "Tsai, Si-Han"

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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.
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
;
Huang, Chiung-Yi
;
Horng, Ray-Hua
;
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.