San-Lein Wu

Nonvolatile Bio-Memristor Fabricated with Egg Albumen Film

This study demonstrates the fabrication and characterization of chicken egg albumen-based bio-memristors. By introducing egg albumen as an insulator to fabricate memristor devices comprising a metal/insulator/metal sandwich structure, significant bipolar resistive switching behavior can be observed. The 1/f noise characteristics of the albumen devices were measured, and results suggested that their memory behavior results from the formation and rupture of conductive filaments. Oxygen diffusion and electrochemical redox reaction of metal ions under a sufficiently large electric field are the principal physical mechanisms of the formation and rupture of conductive filaments; these mechanisms were observed by analysis of the time-of-flight secondary ion mass spectrometry (TOF-SIMS) and resistance–temperature (R–T) measurement results. The switching property of the devices remarkably improved by heat-denaturation of proteins; reliable switching endurance of over 500 cycles accompanied by an on/off current ratio (Ion/off) of higher than 103 were also observed. Both resistance states could be maintained for a suitably long time (>104 s). Taking the results together, the present study reveals for the first time that chicken egg albumen is a promising material for nonvolatile memory applications.

GaN-Based Schottky Barrier Photodetectors With a 12-Pair Mg

GaN-based ultraviolet (UV) photodetectors (PDs) separately prepared with a conventional single low-temperature (LT) GaN buffer layer and a 12-pair Mg_xN_y-GaN buffer layer were both fabricated. It was found that we could reduce threading dislocation (TD) density and thus improve crystal quality of the GaN-based UV PDs by using the 12-pair Mg_xN_y-GaN buffer layer. With a -2-V applied bias, it was found that the reverse leakage currents measured from PDs with a single LT GaN buffer layer and that with a 12-pair Mg_xN_y-GaN buffer layer were 4.57 times 10^-6 and 1.44 times 10^-12 A, respectively. It was also found that we could use the 12-pair Mg_xN_y-GaN buffer layer to suppress photoconductive gain, enhance UV-to-visible rejection ratio, reduce noise level, and enhance the detectivity.

_{\rm x}

The deposition of copper oxide onto vertically well-aligned n-ZnO nanowires by sputtering and the fabrication of p-copper oxide/n-ZnO coaxial nanowire photodiodes are reported. It was found that we could change the copper oxidation number to obtain Cu₂O/ZnO nanowire photodiode, Cu₄O₃/ZnO nanowire photodiode and CuO/ZnO nanowire photodiode by simply changing the O flow rate during deposition. It was also found that noise equivalent powers were 6.1 × 10^-11, 3.8 × 10^-10, and 7.2 × 10^-8 W while normalized detectivities were 6.35 × 10⁹, 1.02 × 10⁹, and 5.37 × 10⁶ cmHz^0.5 W^-1 for the fabricated Cu₂O/ZnO nanowire photodiode, Cu₄O₃ /ZnO nanowire photodiode and CuO/ZnO nanowire photodiode, respectively.

N

This paper reports the influences of uniaxial mechanical stress on the reverse-biased source/drain to substrate junction leakage of state-of-the-art 65 nm CMOS transistors. For n-channel metal-oxide-semiconductor (NMOS) transistors, the band-to-band tunneling (BTBT) dominates the junction leakage current due to heavily doped junction and pocket implants. However, for p-channel metal-oxide-semiconductor (PMOS) transistors with embedded SiGe source/drain, the leakage current is found to result from both BTBT and generation current due to defects generated in the SiGe layer and at the SiGe/Si interface. A four-point bending technique is used to apply mechanical uniaxial stress on NMOS and PMOS devices along the longitudinal direction. It was found that the leakage current of both devices increases (decreases) with applied uniaxial compressive (tensile) stress, and that the strain sensitivity of the junction leakage of NMOS transistors is much weaker than that of PMOS transistors. By combining the bending technique with process strained Si (PSS) technology, additional stress was applied to NMOS and PMOS with high built-in stress to investigate the characteristics of junction leakage under extremely high uniaxial stress. It is shown that uniaxial tensile stress can both enhance the NMOS device performance and decrease the junction leakage. However, for the PMOS, there exists a tradeoff between boosting the transistor performance and decreasing the junction leakage current, so there is a limit in the amount of compressive stress that can be beneficially applied.

_{\rm y}

Here, we present the characteristics of a novel GaN- based ultraviolet (UV) photodiode (PD) with a low-temperature (LT) AIN cap layer. The dark leakage current for the PD with the LT-AIN cap layer was shown to be about four orders of magnitude smaller than that for the conventional PDs. It was found that we could achieve larger UV to visible rejection ratio by inserting an LT-AIN cap layer. It was also found that we could improve minimum noise equivalent power and maximum normalized detectivity of the PD by inserting an LT-AIN cap layer.

–GaN Buffer Layer

A Schottky barrier photodetector with ZnO nanorods is fabricated on a glass substrate and the I-V characteristics are investigated. The ZnO nanorods are synthesized by an aqueous method, which allowed the fabricated Schottky barrier photodetector to be more sensitive in the UV region. Under 370-nm illumination, the photocurrent of the ZnO nanorod Schottky barrier photodetector is 6.56 μA and the UV-to-visible ratio is 780.8 at -1V. In addition, the noise equivalent power and normalized detectivity (D*) of the photodetector are 6.74×10-13 W and 3.29 ×1011 cmHz0.5W-1 at -1V, respectively.

Fabrication and Characterization of Coaxial p-Copper Oxide/n-ZnO Nanowire Photodiodes

This study presents the fabrication of ZnO nanosheets on a glass substrate using a room-temperature (approximately 25 °C) solution method. The average length and diameter of the ZnO nanosheets were 1.2 μm and approximately 5 nm, respectively. The ultraviolet (UV)-to-visible rejection ratio of the sample is approximately 42 when biased at 1 V, and the fabricated UV photodetector is visible-blind with a sharp cutoff at 370 nm. The transient time constants measured during the rise time and fall time were τr = 5.37 s and 6.02 s, respectively. The low-frequency noise spectra obtained from the UV photodetector were caused purely by the 1/ f noise. The noise-equivalent power and normalized detectivity ( D^*) of the ZnO nanosheet photodetector were 6.12 × 10 ^-9W and 2.17 × 10 ⁹ cm·Hz ^0.5 W ^-1, respectively.

The Effects of Mechanical Uniaxial Stress on Junction Leakage in Nanoscale CMOSFETs

GaN-based metal-semiconductor-metal ultraviolet photodetectors (PDs) prepared on a patterned sapphire substrate (PSS) and a conventional flat sapphire substrate were both fabricated and characterized. It was found that we can reduce dark leakage current and enhance by about two orders of magnitude by using a PSS. The internal gain of the PDs prepared on a PSS was also much smaller.

Low-Noise and High-Detectivity GaN UV Photodiodes With a Low-Temperature AlN Cap Layer

The use of low-frequency (1/f) noise to evaluate stress-memorization technique (SMT) induced-stress in n-channel metal-oxide-semiconductor field-effect transistors is investigated. Through observing Hooge’s parameter αH, we found that the unified model can properly interpret the 1/f noise mechanism in our device. On the other hand, lower normalized input-referred noise (LSVG) level in number-fluctuation-dominated regime (region I) and smaller curvature of LSVG versus VGS-VTH in mobility-fluctuation-dominated regime (region II) are attributed to the reduced tunneling attenuation length and Coulomb scattering coefficient, respectively. It represents an intrinsic benefit of 1/f noise behavior stemming from SMT-induced more strain in short channel device.

Low-Frequency Noise Characteristics of ZnO Nanorods Schottky Barrier Photodetectors

ZnO nanorod metal-semiconductor-metal photodetectors prepared on flexible polyimide substrate have been fabricated and investigated in this study. The ZnO nanorod was selectively synthesized between the gap of interdigitated contact by aqueous method and lithography technique. Compared with the conventional ZnO film photodetectors, the ZnO nanorod photodetectors have higher wavelength responsivity. This phenomenon can be attributed to high surface-to-volume ratio of nanorod, which provide an efficient light trapping absorption and enhance the adsorption and desorption rates of oxygen at the ZnO nanorod surface. Under a 1 V applied bias, noise equivalent power and normalized detectivity (D*) were 1.72×10-11 W and 3.08 × 1011 cmHz0.5 W-1, respectively, for the ZnO nanorod photodetector.