Ping-Yu Kuei

Growth Evolution of ZrO2 from Deposited Zr Metal during Thermal Oxidation

This work reveals how oxidation temperature affects the diffusion of Zr, the reaction behavior of oxygen and silicon atoms in the interior stacked layer structure and the corresponding crystalline phase of oxide. The depth distributions of the three important inclusive atoms Zr, O, and Si are experimentally determined.

Dorsal hand vein recognition based on 2D Gabor filters

Abstract Hand vein patterns are among the biometric traits being investigated today for identification purposes, attracting interest from both the research community and industry. A reliable and robust personal verification approach using dorsal hand vein patterns is presented in this paper. This approach needs less computational and memory requirements and has a higher recognition accuracy than similar methods. In our work, a near-infrared charge-coupled device camera is adopted as an input device for capturing dorsal hand vein images, due to its advantages of the low-cost and non-contact imaging. In the proposed approach, two finger-peaks are automatically selected to define the region of interest in the dorsal hand vein images. In order to obtain effective pattern of dorsal hand vein vascular, we proposed an innovative and robust adaptive Gabor filter method to extract the dorsal hand vein patterns and encode the vein features in bit string representation. The bit string representation, called VeinCode, offers speedy template matching and enables more effective template storage and retrieval. The similarity of two VeinCodes is measured by normalised Hamming distance. A total of 6160 dorsal hand vein images were collected from 308 persons to verify the validity of the proposed dorsal hand vein recognition approach. High accuracies (>99%) have been obtained by the proposed method, and the speed of the method (responding time <0·8 s) is rapid enough for real-time recognition. Experimental results demonstrate that our proposed approach is feasible and effective for dorsal hand vein recognition.

Properties of Thermal Gadolinium Oxide Films on Silicon

The formation and electrical characteristics of thermal gadolinium (Gd) oxide films were investigated. A good uniform interface formed by proper treatment was observed by transmission electron microscopy (TEM) examination. The dielectric constant of the thermal Gd oxide films was approximately 10 from capacitance–voltage measurements. The X-ray diffraction (XRD) pattern of the thermal Gd oxide (Gd2O3) films showed that they had a cubic structure. The Gd oxides that were oxidized at higher temperatures exhibited smaller grain boundaries than those oxidized at lower temperatures. The grain boundary size of the Gd oxides significantly affects the leakage property. A good Gd oxide quality can be obtained when the thermal oxidation temperature is above 900°C.

Hysteresis in gadolinium oxide metal-oxide-semiconductor capacitors

This investigation explores how oxidation affects the gadolinium oxide capacitor and the corresponding Gd2O3 hysteresis phenomenon. The current-voltage varied with Gd2O3 thickness and a charged capacitance voltage (C-V) curve with a left shift is also observed in experimental results. The breakdown voltages rise with increasing oxidation time, while the corresponding C-V hysteresis gaps decrease with increasing oxidation time.

Palladium Diffusion Transport in n-Type GaAs

The aim of this study is to determine the diffusion coefficient of palladium (Pd) in gallium arsenide under different annealing conditions. The extent of diffusion was characterized using the secondary ion mass spectrometry (SIMS) technique. The temperature-dependent diffusion coefficients of Pd are 8.4×10-13, 2.25×10-12, and 9.51×10-12 cm2/s, respectively, at temperatures of 400, 550, and 850 °C. The Pd diffusion constant and activation energy in GaAs are calculated as 3.54×10-10 cm2/s and 0.35 eV, respectively. This indicates that the major diffusion mechanism of Pd in GaAs is interstitial diffusion.

Study of AlGaInP multiquantum-well/double heterostructure light-emitting diodes with In-added GaP window layer regrown by antimony-based liquid phase epitaxy

The characteristics of surface-emitting AlGaInP multiquantum-well (MQW) and double heterostructure (DH) light-emitting diodes (LEDs) with a GaP window layer regrown by a GaP source melt with the addition of indium in the liquid phase epitaxy (LPE) system are studied. Using antimony in the source melt instead of gallium eliminates the phenomenon of melt back at the top layer of the LED during the LPE regrowth process. Meanwhile, adding In and Zn to the source melt significantly increases the GaP growth rate and effectively reduces residual melt during the regrowth process. Thus, the AlGaInP LED with a Zn-doped GaP window layer regrown by In being added, Sb-based LPE exhibits a lower turn-on voltage and higher light output power than that without the regrown GaP window layer. However, the emission peak wavelength of the MQW LED shifts a little after the LPE regrowth process. The DH LED does not shift. Thus, the DH structure is more suitable than the MQW structure for the LPE regrowth process of GaP.

Gaussian directional pattern for dorsal hand vein recognition

Abstract With the increasing needs in security systems, hand vein recognition is reliable as one of the important solutions for biometrics-based identification systems. This work presents an effective approach for dorsal hand vein recognition by analysing vein patterns. The methodology involves extraction of dorsal hand vein features based on Gaussian filter. In order to obtain effective pattern of dorsal hand vein vascular, we propose an innovative and robust Gaussian directional filter method to extract the dorsal hand vein patterns and to encode the vein features in binary code. A new coding scheme, namely Gaussian directional binary code, is then proposed for dorsal hand vein recognition. To evaluate the efficacy of the proposed approach, the normalised Hamming distance used in recognition is adopted. A total of 5120 dorsal hand vein images were collected from 256 persons to verify the validity of the proposed dorsal hand vein recognition approach. High accuracies (>99%) and low equal error rate (0·95%) have been obtained by the proposed method. Experimental results demonstrate that our proposed approach is feasible and effective for dorsal hand vein recognition.

Improvement of Surge Protection by Using an AlGaN/GaN-Based Metal-Semiconductor-Metal Two-Dimensional Electron Gas Varactor

In this paper, a varactor with metal–semiconductor–metal diodes on top of the (NH4)2S/P2S5-treated AlGaN/GaN two-dimensional electron gas epitaxial structure (MSM-2DEG) is proposed to the surge protection for the first time. The sulfur-treated MSM-2DEG varactor properties, including current–voltage (I–V), capacitance–voltage (C–V), and frequency response of the proposed surge protection circuit, are presented. To verify its capability of surge protection, we replace the metal oxide varistor (MOV) and resistor (R) in a state-of-the-art surge protection circuit with the sulfur-treated MSM-2DEG varactor under the application conditions of system-level surge tests. The measured results show that the proposed surge protection circuit, consisted of a gas discharge arrester (GDA) and a sulfur-treated MSM-2DEG varactor, can suppress an electromagnetic pulse (EMP) voltage of 4000 to 360 V, a reduction of 91%, whereas suppression is to 1780 V, a reduction of 55%, when using only a GDA.

Temperature Characteristics of High Modulation Rate Platinum-Diffused AlGaInP Resonant-Cavity Light-Emitting Diodes

This study is focused on the temperature characteristics of platinum-diffused AlGaInP resonant-cavity light-emitting diodes (RCLED). The shape of the platinum-diffused AlGaInP RCLED emission spectra and the full width at half maximum (FWHM) of the main electroluminescent (EL) spectra are almost uninfluenced over the measured temperature range of 20 to 100 ?C. Therefore, the platinum-diffused devices show a high characteristic temperature, and a small temperature shift in the peak emission wavelength.

Oxygen and Hydrogen Implanted Oxidation Enhancement of Al0.98Ga0.02As/Al0.7Ga0.3As Distributed Bragg Reflector Structure

This study investigates the lateral oxidation enhancement of Al0.98Ga0.02As/Al0.7Ga0.3As distributed Bragg reflector (DBR) structure layers implanted with either oxygen or hydrogen ions. The results revealed that the lateral oxidation rate of Al0.98Ga0.02As/Al0.7Ga0.3As DBR layers with oxygen-implantation was higher than that in the case without oxygen-implantation, but hydrogen implantation in Al0.98Ga0.02As/Al0.7Ga0.3As DBR layers did not lead to an oxidation enhancement phenomenon. A high oxidation rate can shorten the oxidation time or lower the oxidation temperature, and thus would aid in increasing DBR performance and reliability.