Browsing by Author "Chen, Chung-Le"

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Effect of UV illumination on inverted-staggered a-Si : H thin film transistors
(2007)
Li, Yiming
;
Lou, Jen-Chung
;
Chen, Chung-Le
;
Hwang, Chih-Hong
;
Yan, Shuoting
The hydrogenated amorphous silicon thin-film transistors (a-Si:H TFT's) have been widely used as switching devices for large-area electronics, such as active matrix liquid crystal displayers. Effect of UV Illumination on improving device switching characteristics has been experimentally observed and studied. However, the inside mechanisms including state and density of traps, are not clear yet. In this work, to characterize the optimal device characteristics, we thus solve a set of Poisson, electron/hole continuity, and lattice heat flow equations coupling with density and distribution of trap states in the a-Si:H layer. The I-V characteristics of the inverted staggered a-Si:H TFT's with different magnitude of UV light illumination is for the first time calculated and carefully calibrated with experimental measured data. It is found that the traps states in the a-Si:H layer and the movement of Fermi level from the conduction band after UV illumination. This study provides an insight into the effect of UV illumination and the mechanism to improve the switching characteristics of a-Si TFTs.
UV Illumination Technique for Leakage Current Reduction in a-Si:H Thin-Film Transistors
(2008-11-01)
Li, Yiming
;
Hwang, Chih-Hong
;
Chen, Chung-Le
;
Yan, Shuoting
;
Lou, Jen-Chung
The high photoconductivity of hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs) is responsible for the leakage current under illumination-particularly in projectors and displays with high-intensity backlight illumination. This work investigates a leakage current reduction approach, in which the inverted staggered a-Si:H TFTs are exposed to the ultraviolet (UV) laser. An 85% reduction in the leakage current in a-Si:H TFTs is experimentally observed. The general SPICE model (such as the RPI model) lacks the proper term to capture the photo-induced phenomena; therefore, the physical mechanisms that are associated with the illumination of a-Si:H TFTs under UV, including the energy state and the density of traps, are analyzed using device simulation. The I-V characteristics of the inverted staggered a-Si:H TFTs under different magnitudes of UV exposure are calibrated with experimentally measured data. The preliminary results show the change of trap states in amorphous silicon film and a shift of the Fermi level with UV illumination. UV illumination may induce traps in the active layer of the device and thereby reduce the OFF-state leakage current.