Browsing by Author "Lai, Chih-Ming"

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Comparison between extended microtunnels along different crystal orientations in GaN
(2008)
Wu, Pei-Lun
;
Huang, Hsin-Hsiung
;
Zeng, Hung-Yu
;
Liu, Po-Chun
;
Lai, Chih-Ming
Triangular prism-like extended microtunnels (EMTs) can be easily formed in specially designed cpitaxial lateral overgrowth GaN thick films by selective wet chemical etching in molten potassium hydroxide (KOH), In this study, extended microtunnels along the < 1100 > and the < 1120 > directions were fabricated and compared. If tunnels along the < 1100 > direction, the (1122) planes would be the etch stop plane. While the tunnels along < 1120 > direction, the etch stop plane would become to (1011) planes. The activation energies of wet chemical etch for the {1122} planes and the (1011) planes were determined to be 23.6 kcal/mol (1.02 eV) and 22.8 kcal/mol (0.99 eV) using Arrhenius plot. On the other hand, the etching depths of the tunnels along the < 1100 > direction were more than twice the depths of the tunnels along the < 1120 > direction during the same etching time. The highest etch rate of the tunnels along the axial direction can reach 1000 mu m/hr in < 1100 > direction, which is believed to be the highest etch rate of GaN ever reported. Additional crystal facet of m-plane in GaN was also observed in the sample with extended microtunnels along the < 1120 > direction. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Effects of Mechanical Strains on the Characteristics of Top-Gate Staggered a-IGZO Thin-Film Transistors Fabricated on Polyimide-Based Nanocomposite Substrates
(2012-07-01)
Lin, Chang-Yu
;
Chien, Chih-Wei
;
Wu, Chung-Chih
;
Yeh, Yung-Hui
;
Cheng, Chun-Cheng
In this paper, we had successfully implemented flexible top-gate staggered amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) on colorless and transparent polyimide (PI)-based nanocomposite substrates using fully lithographic and etching processes that are compatible with existing TFT mass fabrication technologies. The use of the selectively coated release layer between the nanocomposite PI film and the glass carrier ensured smooth debonding of the plastic substrate after TFT fabrication. The TFTs showed decent performances (with mobility > 10 cm(2)/V . s) either as fabricated or as debonded from the carrier glass. By bending the devices to different radii of curvature (from a flat state to an outward bending radius of 5 mm), influences of mechanical strains on the characteristics of flexible a-IGZO TFTs were also investigated. In general, the mobility of the flexible a-IGZO TFT increased with the tensile strain, whereas the threshold voltage decreased with the tensile strain. The variation of the mobility in a-IGZO TFTs versus the strain appeared smaller than those observed for amorphous silicon TFTs.
Self-separated freestanding GaN grown on patterned substrate by hydride vapor phase epitaxy
(2007)
Lai, Chih-Ming
;
Liu, Wen Yu
;
Tsay, Jenq-Dar
;
Liu, Po Chun
;
Guo, Yih-Der
A freestanding Gallium Nitride bulk is obtained without using laser lift-off technology. Two techniques such as mask-less ELOG and air-bridge structure are applied on patterned substrate. A self-separated result is successfully demonstrated by using mask-less ELOG and air-bridge structure. Due to the thermal coefficient of expansion (TCE) mismatch between the GaN layer and the non-native (foreign) substrate, separation happens during cooling down after HVPE growth. Both two structures successfully help to lift GaN off the substrate. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.