Browsing by Author "Lee, M. H."

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Device Instability of ReRAM and a Novel Reference Cell Design for Wide Temperature Range Operation
(2017-09-01)
Lin, Y. H.
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Lin, Y. Y.
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Lee, F. M.
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Ho, Y. H.
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Hsu, K. C.
This letter addresses two difficult challenges for transition metal oxide resistive random access memories (ReRAMs)-sensitivity to operation temperature and random fluctuation of resistance value. A careful study of a WOx ReRAM array reveals that these devices are unstable and their read currents fluctuate with time due to random telegraph noise and structure relaxation. Consequently, even after careful programming, the current distribution can broaden with time and tail bit population grows. Furthermore, ReRAM state is sensitive to temperature and a reference cell made of the same device material must be used. Thus, although the broadening of read current distribution may be tolerated by creating a larger RESET/SET memory window, the current fluctuation still makes it impossible to predict the output of the reference cell, leading to array malfunction. This letter investigates the current (resistance) instability in detail and proposes a reference array with a novel trimming method that can stabilize the reference current level. The proposed reference array has very good dc stress reliability as well as wide-range temperature tracking performance from -40 degrees C to 85 degrees C.
PDMS-based flexible energy harvester with Parylene electret and copper mesh electrodes
(2015-10-01)
Chiu, Y.
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Lee, M. H.
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Wu, S-H
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電機資訊學士班
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Undergraduate Honors Program of Electrical Engineering and Computer Science
Currently, most vibrational energy harvesters have rigid and resonant structures to scavenge kinetic energy from periodic motion in specific directions. However, in some situations the motion is random in amplitude, frequency, and direction; or the targeted energy sources apply direct deformation or displacement to the harvesters. In these applications, flexible energy harvesters that are light, flat, and conformable to arbitrary 3D surfaces of the sources are desired to scavenge the energy from device deformation, rather than the motion of a moving mass. Therefore we propose and demonstrate a PDMS-based flexible energy harvester with Parylene-C electret that can be attached to deformable surfaces. Furthermore, copper mesh is embedded in the flexible electrodes for robust electrode metallization as compared with traditional sputtered metal thin films. The fabricated harvesters achieved net output power of 2.2 mu W, area power density of 2.2 mu W cm(-2), and volume power density of 22 mu W cm(-3) at the maximum test frequency of 20 Hz. Power generation by finger tapping and bending was demonstrated. Such harvesters have the potential for wearable and implantable electronic applications.
The Guideline on Designing Face-tunneling FET for Large-scale-device Applications in IoT
(2017-01-01)
Hsieh, E. R.
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Lee, J. W.
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Lee, M. H.
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Chung, Steve S.
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電子工程學系及電子研究所
A thorough understanding on how to design and to manufacture a face-tunneling TFET (f-TFET) has been provided. By taking advantage of an area-tunneling, in comparison to conventional point-tunneling FET, f-TFET can be enhanced in its I-on current. This work shows Ion of f-TFET with one-order magnitude Ion enhancement than that of point-TFET(control), and the longer the gate length is, the higher the Ion becomes. However. from experimental results, S.S. of f-TFET is a little worse than that of control and shows strong dependency on temperature because of dominance of trap-assisted tunneling. To understand how traps affect I-on of f-TEFT, the charge-pumping measurement is utilized to examine trap distributions in the tunneling region. The results show that the channel/source interfacial traps degrade the performance of f-TFET, however, with careful treatment of the epi-process of f-TFET, this device with face-tunneling shows great potential for future IoT applications.