[en] The switching time-voltage dependence of electronic resistive switching was studied for understanding the switching dynamics in Pt-dispersed SiO2 thin film devices. Trapezoidal voltage pulses with opposite polarities were consecutively introduced and thereby transient on-switching and off- switching were examined. A prior on-switching voltage determines the off-switching voltage regardless of the sweeping rate of the pulse for the prior on-switching. However, the off-switching voltage was sensitive to the sweeping rate of the subsequent pulses for off-switching. The frequencydependent impedance of both the device and the surrounding circuit element are thought to result in the variation of the off-switching voltage; otherwise, the switching voltage is independent of time.

[en] High-density nonvolatile memories can be realized by fabricating resistive random-access memories (RRAMs) as 4F${}^2$ (F: minimum feature size) cells in a crossbar array (CBA) configuration. However, the CBA configuration induces leakage currents in the nearby cells, which significantly reduces the read-out margin and limits the CBA size extension. One solution to this problem is to integrate an RRAM with a bidirectional selector. Research on the various type of selector devices has been extensively explored so far, however, a device that satisfies all requirements has not been developed. In this paper, we propose a novel bidirectional diode selector with a Pt/HfN${}_x$/Pt stack. We implement a one-selector-one-resistor configuration in a 10 × 10 CBA by integrating Pt/HfN${}_x$/Pt with a Ti/HfO${}_2$/Pt RRAM stack. We confirm the stable resistive switching operation and good thermal stability of the selector and its integrated device. Chemical analyses aided by Auger electron spectroscopy and X-ray photoelectron spectroscopy reveal the gradient-oxidation of the HfN${}_x$ film, which explains the nonlinear and asymmetric current-voltage characteristics. This novel nonlinear selector with simple structure and high thermal stability can be applied to build CBAs for high-density nonvolatile memories or neuromorphic computing elements, in the future.

[en] The temperature-dependent electrical properties of Au/GaN Schottky diodes with an Al2O3 layer prepared by using atomic layer deposition (ALD) were investigated. Compared to the Au/GaN junction, the Au/Al2O3/GaN junction was found to have lower barrier heights and higher ideality factors. For the Au/GaN junction, the native oxide and the thin surface barrier formed by surface states caused a large leakage current and a small capacitance. Due to surface passivation through the ALD process, the leakage current for the Au/Al2O3/GaN junction was reduced. The barrier height reduction for the Au/Al2O3/GaN junction was associated with interface dipole formation at the Al2O3/GaN interface.

[en] The advent and wide use of antibiotics have decreased the incidence of deep neck infection. When a deep neck infection does occur, however, it can be the cause of significant morbidity and death, resulting in airway obstruction, mediastinitis, pericarditis, epidural abscesses, and major vessel erosion. In our clinic, a patient with diffuse chronic osteomyelitis of mandible and fascial space abscess and necrotic fasciitis due to odontogenic infection at the time of first visit came. We successfully treated the patient by early diagnosis using contrast-enhanced CT and follow up dressing through the appropriate use of radiographic images.

[en] We investigated the effect of an Al₂O₃ interfacial layer grown by atomic layer deposition on the electrical properties of Au Schottky contacts to n -type InP. Considering barrier inhomogeneity, modified Richardson plots yielded a Richardson constant of 8.4 and 7.5 Acm⁻²K⁻², respectively, for the sample with and without the Al₂O₃ interlayer (theoretical value of 9.4 Acm⁻²K⁻² for n -type InP). The dominant reverse current flow for the sample with an Al₂O₃ interlayer was found to be Poole–Frenkel emission. From capacitance–voltage measurements, it was observed that the capacitance for the sample without the Al₂O₃ interlayer was frequency dependent. Sputter-induced defects as well as structural defects were passivated effectively with an Al₂O₃ interlayer. (paper)

[en] Highlights: • AlN passivation effect on Au/GaN Schottky junctions were investigated. • Sample with an AlN layer showed higher barrier height and lower ideality factor. • Lower interface state density was obtained with an AlN layer. • Surface passivation by AlN layer improved the interface quality. -- Abstract: Surface passivation effect with an aluminum nitride (AlN) thin film deposited by atomic layer deposition (ALD) on metal/gallium nitride (GaN) junctions were investigated using current–voltage and capacitance–voltage (CV) measurements. The sample with an AlN layer revealed higher barrier height and lower ideality factor compared to the sample without AlN layer. X-ray photoelectron spectroscopy measurement on bare GaN surface showed the presence of native oxide on the GaN surface. From CV measurements, it was found that the interface state density was reduced with an AlN layer. Hence, deposition of AlN layer by ALD can be used to improve the interface quality of metal/GaN junction.

[en] In this work, we investigated the interfacial properties of AlN/GaN heterostructure with HfO₂/Al₂O₃ (single bilayer) and HfO₂/Al₂O₃/HfO₂/Al₂O₃ (double bilayer) dielectrics prepared by atomic layer deposition (ALD). From capacitance–voltage measurements, significant frequency dispersion was observed for the single bilayer. The interface traps for the double bilayer showed the exponential dependence of trap time constant to the applied voltage, indicating the high quality and uniform interface, whereas the single bilayer deviated from this dependence, revealing the non-uniformity of oxide charges. According to current–voltage measurements, the double bilayer showed much lower leakage current than the single bilayer. X-ray photoelectron spectroscopy measurements showed that Hf–Al–O bonding formed wider region for the double bilayer. For the single bilayer, the outdiffusion of Ga atoms into the AlN layer and the formation of Al–OH were observed more significantly. This work indicates that the double bilayer is a promising dielectric on the AlN/GaN heterostructure. (paper)

[en] The detailed mechanism of electronic bipolar resistance switching (BRS) in the Pt/TiO₂/Pt structure was examined. The conduction mechanism analysis showed that the trap-free and trap-mediated space-charge-limited conduction (SCLC) governs the low and high resistance state of BRS, respectively. The SCLC was confirmed by fitting the current-voltage characteristics of low and high resistance states at various temperatures. The BRS behavior originated from the asymmetric potential barrier for electrons escaping from, and trapping into, the trap sites with respect to the bias polarity. This asymmetric potential barrier was formed at the interface between the trap layer and trap-free layer. The detailed parameters such as trap density, and trap layer and trap-free layer thicknesses in the electronic BRS were evaluated. This showed that the degradation in the switching performance could be understood from the decrease and modified distribution of the trap densities in the trap layer.

[en] A replacement of high-k process was implemented on an independent double gate FinFET, following the ordinary gate-first process with minor modifications. The present scheme involves neither exotic materials nor unprecedented processing. After the source/drain process, the sacrificial gate oxide was selectively substituted with amorphous Ta₂O₅ via conformal plasma enhanced atomic layer deposition. The present gate-first gate-dielectric-last scheme combines the advantages of the process and design simplicity of the gate-first approach and the control of the effective gate workfunction and the interfacial oxide of the gate-dielectric-last approach. Electrical characterization data and cross-sectional images are provided as evidence of the concept. (fast track communication)

[en] This study examined the effects of the composition and microstructure on the electric resistivity of Ge-doped Sb phase change thin films grown by cyclic plasma enhanced chemical vapor deposition. Ge and Sb layers were deposited sequentially to form either a Ge_xSb_y mixture or Ge/Sb nanolaminated films. While the resistivity of the nanolaminated films was higher, the Ge_xSb_y mixture showed a lower resistivity than the pure Sb film. This can be explained by the increase in carrier density of the alloy, as confirmed by first-principles calculations. An abrupt change in resistance accompanying a phase change was observed at ∼210 deg. C.