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As a transmitter power amplifier (PA), the electrical output characteristics of gallium nitride (GaN) high electron mobility transistors (HEMTs) are closely related to the drain current versus drain voltage (${I}_{d}$ – ${V}_{d}$) characteristics. Any abnormalities in the ${I}_{d}$ – ${V}_{d}$ characteristics will seriously affect device performance. Therefore, many groups have investigated the kink effect of GaN HEMTs. One of the commonly used measurement methods of the kink effect is the ${I}_{d}$ – ${V}_{d}$ forward and reverse sweep. In this study, we used the same method for Al2O3/Si3N4–AlGaN/GaN metal–insulator–semiconductor HEMT (MIS HEMT) devices. We found that not only did the kink effect occurred but ${I}_{d}$ also increased abnormally during the reverse sweep and after a series of electrical measurements. At the end of the forward sweep, impact ionization caused by a high ${V}_{d}$ generated electron–hole pairs and some holes accumulated under the gate region, which caused the negative shift of the threshold voltage (${V}_{\text{Th}}$), leading to an abnormal increase in ${I}_{d}$ during the reverse sweep. [ABSTRACT FROM AUTHOR]

To control the parasitic conduction between devices, photolithography and dry etching of organic thin-film transistors (OTFTs), which utilize the gate metal as a hard-mask for organic semiconductor (OSC) patterning, are used. This study shows that the hard-mask patterning process results in a gate leakage current, which is attributed to the sidewall defects. The characteristic mechanisms of different leakage currents were studied to understand this behavior, including negative-bias temperature stress (NBTS) testing and measurements of devices with structural asymmetry. Additionally, an optimized structure design is proposed to suppress the leakage and increase the reliability of OTFTs. Such improvements are necessary for practical applications of OTFTs requiring small channel widths, such as displays and logic circuitry. [ABSTRACT FROM AUTHOR]

In this study, dual-gate thin-film transistors with low-temperature polysilicon as the active channel layer are thoroughly investigated. Under a large current operation where a high voltage is applied, impact ionization occurs near the drain, generating a large number of electron-hole pairs. Owing to the positive bias applied to the gate and drain, holes accumulate on the backside of the channel, which causes an earlier turn-on in the sub-channel, as is observed in the I-V characteristics of the saturation region. By enlarging the highly doped region between the double gates in the channel, the threshold voltage shift can be completely suppressed, and the leakage current rise can be reduced. The electric field simulation using Silvaco TCAD was consistent with the experimental results. Finally, a series transistor structure is used to measure the impact after the operation condition and further verify the physical model. [ABSTRACT FROM AUTHOR]

According to previous research, supercritical fluid nitridation (SCFN) treatment yields only a limited improvement in AlGaN/GaN high-electron-mobility transistors due to the additional water molecules generated during the SCFN treatment, which reacts with dangling bonds of AlGaN/GaN causing undesirable oxidation, thereby affecting the reliability of the device. In this study, we performed an annealing (ANL) treatment post the SCFN treatment to obtain an ANL-SCFN device with improved electrical performance, owing to the fact that the ANL treatment decreases the gate current leakage and increases the reliability of the device. Furthermore, to verify the decrease in the number of defects in the AlGaN layer of the device after ANL, we conducted a reliability analysis of the negative bias voltage stress (NBS) to observe the deterioration in the output of the device. Previous studies state that the electrons generated through NBS trap the defects in the AlGaN layer, thereby decreasing the electrical properties of the device. However, this study showed that the degradation of the ANL-SCFN device reduced significantly after the NBS analysis, considering the amount of OFF-state leakage decreased due to the ANL treatment, which improved the switching characteristics of the device. [ABSTRACT FROM AUTHOR]

In this work, three MISHEMT devices with different electric-field-dispersion layer (EDL) behave the same pristine electrical properties. EDL, which is low dielectric constant (low-k), can effectively disperse electric field, which enhances breakdown voltage and improves reliability in MISHEMT. In a comparison of devices with high-k and low-k EDL, the on-state current ($\text{I}_{\mathrm{ on}}$) of the high-k EDL devices is more significantly reduced than low-k EDL devices after off-state stress. A model for the dispersion of electric fields by the EDL is proposed for this interesting phenomenon. The distribution of the electric field is verified by Silvaco electric field simulation. Finally, the breakdown voltages of the three devices were measured, confirming that the devices with a low-k EDL can increase their breakdown voltages by an additional 600 V, which is 250 % higher than that in the high-k EDL device. [ABSTRACT FROM AUTHOR]

This study investigates an improvement in memory characteristics through depositing an In2O3 layer as an oxygen ion reservoir in the switching layer (SL) of resistive random access memory (RRAM). The deposition of In2O3, denoted as Pt/HfO2/In2O3/TiN device, provides better memory characteristics including lower forming voltage (VF), set/reset voltage (VSET/VRESET), larger memory window, and higher resistances with higher uniformity at low resistance state (LRS) and high resistance state (HRS), compared to the devices without the In2O3 deposition, denoted as Pt/HfO2/TiN device. The conduction mechanisms, verified through fitting current–voltage (I - V) curves, are consistent with the results of a varied temperature I - V experiment. Finally, a physical model is proposed to explain our observations. [ABSTRACT FROM AUTHOR]

This research investigates one of the process or element doping methods used to enhance the reliability of resistive random access memory (RRAM). A supercritical fluid process combines the advantages of the high permeability of gas with the solubility of liquids, and this novel process introduces water molecules into the supercritical fluid for oxidation in order to improve the resistance of random storage. In terms of reliability of the memory, while previous research has used an oxygen plasma treatment to improve RRAM device performance, this work performed a comparison of the two methods and found that the supercritical oxidation treatment can reduce the forming voltage by 25% and produce superior electrical operation, with an endurance test exhibiting an increase to 108 cycles and an improvement of 102. The material analysis confirmed that, during the resistance switching process, the switching layer was more oxidized after this novel supercritical oxidation, resulting in the reduction of operating current and improved reliability compared with the plasma oxidation device. [ABSTRACT FROM AUTHOR]

In this article, an n-type double-gate low-temperature polysilicon (LTPS) TFT is investigated. Previous work has confirmed that the hot-carrier effect will cause impact ionization. Here we observed that, after hot-carrier stress (HCS), the transfer curve in the saturation region has a negative $\text{V}_{\mathrm {th}}$ shift, and a hump is also observed. The reverse output characteristic shows that gate induced drain leakage (GIDL) of the transistor gradually increases and the subthreshold swing (S.S.) has a tendency to collapse. In structures with longer lightly doped drain (LDD) lengths, the electric field at both source/drain side can be effectively dispersed. Thereby, an extended LDD can reduce the overall degradation, and a physical model of explanation is proposed. By using the energy band diagram, we clarify how the additional electron hole pairs affect the output property. Next, Silvaco TCAD simulation is utilized to illustrate the electric field distribution and validate the physical model. [ABSTRACT FROM AUTHOR]

In this experiment, the electrical performance of zinc oxide based-resistive random access memory (RRAM) is successfully improved by using annealing in ammonia hydroxide solution at low-temperature and high pressure to complete ammonium-doped ZnO based-RRAM. The results of material analysis indicate that using CO2 as ammonia hydroxide carrier during the annealing process leads to the reduction in dangling bond density. This can be clearly observed in the decrease in breakdown voltage during the forming process and a lower operating current during operation. Furthermore, in this ammonium-doped ZnO based-RRAM, we study the molecular doping of NH3 in ZnO, where the endurance and retention properties are improved as well. These improvements can be attributed to the higher concentration of nitrogen in the switching layer, which can effectively control the active oxygen ions during the operation process. [ABSTRACT FROM AUTHOR]

Based on the alternating direction implicit finite-difference time-domain (ADI-FDTD) algorithm, a higher order perfectly matched layer (HO-PML) is proposed to solve the problems in a three-dimensional computational domain. The proposed scheme can not only take advantage of the HO-PML for improving the absorbing performance but also has the advantage of the ADI-FDTD algorithm in terms of the unconditional stability. A dielectric resonator antenna example is carried out to validate its effectiveness. The results show that the Courant–Friedrich–Levy limit can be eliminated and the absorbing performance can be further enhanced. [ABSTRACT FROM AUTHOR]

Since nearly all studies concerning the approximate Crank–Nicolson perfectly matched layer (CN-PML) are limited to 2-D cases, a computationally efficient implementation that can be used to truncate 3-D finite-difference time-domain (FDTD) lattices is presented in this article. More precisely, it is based on the CN direct-splitting (DS) scheme and the bilinear transform (BT) method. This article can fully exploit the unconditional stability of the standard CN-FDTD method and can be free from the Courant–Friedrich–Lewy (CFL) limit; hence, it is especially suitable for situations where space discretization step is much smaller than 1/10th or 1/20th of the smallest wavelength of interest. Aiming at further reducing the requirement of the computer resources, this new implementation can be reformulated in more simple forms if proper auxiliary variables are introduced. It therefore shows a higher iteration speed than other published unconditionally stable PMLs as fewer numbers of arithmetic operations are involved. Finally, three numerical examples, including scatting, transmission, and radiation, are also provided to validate its running time, unconditional stability, and absorption characteristic. [ABSTRACT FROM AUTHOR]

This article explains the difference in the reset processes between single RRAM and 1T1R RRAM structures. In the single RRAM, as the reset voltage increases, the off-state resistance increases. This is a normal RRAM operation. However, in the 1T1R structure, the reset voltage increases while the OFF-state resistance does not increase. This may be caused by either current or voltage being insufficient to switch the RRAM to its higher resistance state. The measurements of real voltage indicate that the insufficient voltage is in fact the main cause. For the 1T1R RRAM structure, if it is to be reset to a higher resistance state, it is best done by increasing the gate voltage to increase the OFF-state resistance. Therefore, we provide a method to reduce the misjudgment in the array, and it would be beneficial for the development of high-density memory. [ABSTRACT FROM AUTHOR]

This letter developed the high-performance GaN-based light-emitting diodes (LEDs) for ultraviolet (UV) light emission at 385 nm with the light output power enhanced by up to 52% compared with that of the conventional UV-LEDs. The high-power-efficiency UV-LEDs include sidewall-passivated Al2O3 dielectric nanoscale air voids, which were created using the atomic layer deposition method and act as intermediate media for improving the internal quantum efficiency, reducing threading dislocation, and relaxing strain. The fabricated air void nanostructure also enhanced the light extraction efficiency by $\sim 32.7$ %, resulting in a high-power UV light-emitting device. [ABSTRACT FROM AUTHOR]