β-Ga2O3 is an emerging, ultra-wide bandgap (energy gap of 4.85 eV) transparent semiconducting oxide (TSO), which attracted recently much scientific and technological attention. Unique properties of that compound combined with its advanced development in growth and characterization place β-Ga2O3 in the frontline of future applications in electronics (Schottky barrier diodes, field-effect transistors), optoelectronics (solar- and visible-blind photodetectors, flame detectors, light emitting diodes), and sensing systems (gas sensors, nuclear radiation detectors). A capability of growing large bulk single crystals directly from the melt and epi-layers by a diversity of epitaxial techniques, as well as explored material properties and underlying physics, define a solid background for a device fabrication, which, indeed, has been boosted in recent years. This required, however, enormous efforts in different areas of science and technology that constitutes a chain linking together engineering, metrology and theory. The present review includes material preparation (bulk crystals, epi-layers, surfaces), an exploration of optical, electrical, thermal and mechanical properties, as well as device design / fabrication with resulted functionality suitable for different fields of applications. The review summarizes all of these aspects of β-Ga2O3 at the research level that spans from the material preparation through characterization to final devices.

https://iopscience.iop.org/article/10.1088/1361-6641/aadf78/pdf

β-Ga2O3 for wide-bandgap electronics and optoelectronics

Among the important optoelectronic devices, ultraviolet (UV) photodetectors show wide applications in fire monitoring, biological analysis, environmental sensors, space exploration, and UV irradiation detections. Research interest has focused on the utilization of one-dimensional (1D) metal oxide nanostructures to build advanced UV photodetectors through various processes. With large surface-to-volume ratio and well-controlled morphology and composition, 1D metal oxide nanostructures are regarded as promising candidates as components for building photodetectors with excellent sensitivity, superior quantum efficiency, and fast response speed. This article reviews the latest achievements with 1D metal oxide nanostructures reported over the past five years and their applications in UV light detection. It begins with an introduction of 1D metal oxide nanostructures, and the significance, key parameters and types of photodetectors. Then we present several kinds of widely-studied 1D nanostructures and their photodetection performance, focusing on binary oxides with wide-bandgap (such as ZnO, SnO2, Ga2O3, Nb2O5, and WO3) and ternary oxides (such as Zn2SnO4, Zn2GeO4, and In2Ge2O7). Finally, the review concludes with our perspectives and outlook on future research directions in this field.

http://www.thenanoresearch.com/upload/justPDF/0661.pdf

Nanoscale ultraviolet photodetectors based on onedimensional metal oxide nanostructures

With the scaling of process node and increase of operation voltage, the electrical fields and impact ionization generation rates in lateral double-diffused MOS (LDMOS) transistors are obviously increased. As a result, a detailed characterization and understanding for long-term hot-carrier-induced (HCI) effect of LDMOS have been becoming more and more important. This review compares and summarizes the HCI damage locations and degradation mechanisms for all kinds of typical LDMOS devices under different stress conditions. Finally, generalized conclusions on HCI effect of LDMOS are deduced, and some special degradation influence factors brought by the device design technologies are also clarified.

A Review on Hot-Carrier-Induced Degradation of Lateral DMOS Transistor

This paper explores the cold field emission (CFE) properties of SiC nanowire (NW) arrays. The CFE currents were studied in the dark and under ultra-violet (UV) irradiation conditions. An increase in CFE current was observed when the SiC NW arrays were illuminated, with a consequent decrease in the values of the turn-on field and the threshold field. Furthermore, while dark CFE currents were well described by the standard Fowler–Nordheim (FN) theory for metals, the photo-enhanced CFE currents showed nonlinearity in FN plots. Specifically, a voltage range of current saturation appeared, which is appealing for nanotechnological applications, and it is indeed an essential prerequisite for realizing devices such as FE photocathodes.

Cold field electron emission of large-area arrays of SiC nanowires: photo-enhancement and saturation effects

A robust FinFET silicon-controlled rectifier (SCR) LDMOS ESD protection device is developed. Replacing the drain contact implant to the P+ implant from N+ implant creates an SCR inside the LDMOS and when the N+ contact is removed a Schottky SCR LDMOS is created. The ESD performance of the baseline FinFET LDMOS is Zero, while that of the SCR LDMOS is 9.2 mA/ $\mu {\mathrm{ m}}$ and Schottky SCR is 4.6 mA/ $\mu \text{m}$ respectively.

Engineering ESD Robust LDMOS SCR Devices in FinFET Technology

A hybrid fin/planar lateral double-diffused MOSFET (LDMOS) design (hybrid FET) is proposed for the high-voltage input–output devices in a FinFET-based system-on-chip (SoC) technology. 3-D technology computer-aided design simulations show that a planar drift region and a planar drain region are advantageous for higher breakdown voltage (BV) to specific on-state resistance ( ${R}_{\text {on$\_{}$sp}})$ ratio (BV2/ ${R}_{\text {on$\_{}$sp}})$ . By slightly extending the planar portion of the semiconductor active region into the gated channel region, the theoretical limit of BV2/ ${R}_{\text {on$\_{}$sp}}$ for LDMOS can be surpassed. Hybrid FETs can be fabricated using a process flow that is compatible with the state-of-art FinFET SoC technology.

Simulation-Based Study of Hybrid Fin/Planar LDMOS Design for FinFET-Based System-on-Chip Technology

A scheme for precisely adjusting the drive strength of an inserted-oxide FinFET (iFinFET) comprising two nanowire (NW) channel regions that are separated by a thin oxide layer, to enhance the manufacturing yield of a minimally sized six-transistor static random access memory (6T-SRAM) cell, is investigated in this paper. The 3-D process simulations show that the upper NW channel region can be selectively rendered nonconducting by dopant ion implantation followed by thermal annealing so that its threshold voltage is greater than the supply voltage ( ${V}_{\text {DD}}$ ). Furthermore, the position of the inserted-oxide layer can be adjusted to balance the tradeoff between the read stability and write-ability to achieve the lowest minimum cell operating voltage ( ${V}_{\text {min}}$ ). Using a compact transistor model calibrated to 3-D device simulations, doped iFinFET technology is projected to enable ${V}_{\text {min}}$ of a minimally sized 6T-SRAM cell to be substantially lower than ${V}_{\text {DD}}$ , eliminating the need for write-assist circuitry and lowering power consumption.

Simulation-Based Study of High-Density SRAM Voltage Scaling Enabled by Inserted-Oxide FinFET Technology

PbTiO3 was used as a dopant and PbTiO3/titanium dioxide (TiO2) nanofibers (NFs) were used as a scattering layer in the photoanode of dye-sensitized solar cell (DSSC). Their effects on the characteristics of the photoanode of DSSC were studied. The DSSC with the modified photoanode by PbTiO3 and PbTiO3/TiO2 NFs was characterized by X-ray diffractometer (XRD), electrochemical impedance spectroscopy (EIS), <inline-formula> <tex-math notation="LaTeX">${J}$ </tex-math></inline-formula>–<inline-formula> <tex-math notation="LaTeX">${V}$ </tex-math></inline-formula> characterization, and incident photon current efficiency (IPCE) measurement. The results show that PbTiO3 and PbTiO3/TiO2 NFs can improve the photovoltaic characteristics of DSSC photoanode. The DSSC with modified photoanode by PbTiO3/TiO2 NFs shows better photoelectric conversion efficiency (<inline-formula> <tex-math notation="LaTeX">$\eta $ </tex-math></inline-formula>). Compared with the DSSC without modification (TiO2 photoanode), the photovoltaic conversion efficiency (<inline-formula> <tex-math notation="LaTeX">$\eta $ </tex-math></inline-formula>) of the DSSC with modified photoanode by PbTiO3/TiO2 NFs has increased by 19%. Based on this research, it can be considered that PbTiO3/TiO2 NFs can be used as one of the candidate materials to improve the photovoltaic performance of DSSCs.

Photoanode Modified by PbTiO3 or PbTiO3/TiO2 Nanofibers in Dye-Sensitized Solar Cell

This letter presents vapor-liquid-solid growth of β-Ga2O3 nanowires (NWs) on cost-effective SiO2/Si template and the fabrication of β-Ga2O3 NW field emitters. It is found that the β-Ga2O3 NWs grown at 950°C are structurally uniform, defect free, and well-oriented with pure monoclinic structure. It is also found that turnon fields are 2.0, 3.9, and 5.8 V/μm whereas field-enhancement factors β are 1890, 2760, and 4489, for the samples grown at 850°C, 900 °C, and 950°C, respectively. For the sample prepared at 950°C, it is found that we could further reduce the turnon field from 2 to 1.2 V/μm whereas enhance the field-enhancement factor β from 4489 to 6926 by ultraviolet irradiation.

UV Enhanced Field Emission for β-Ga 2 O 3 Nanowires

A scheme for controllably adjusting transistor drive strength in inserted-oxide FinFET (iFinFET) technology is proposed, to enable cell ratio tuning for a minimally sized six-transistor (6T) SRAM cell. Specifically, one or more of the stacked nanowire channels within an iFinFET can be made to be essentially non-conducting by ion implantation to increase its threshold voltage. Via 3-D device simulations and a calibrated compact $I$ – $V$ model, this scheme is projected to enable more than 0.1 V reduction in minimum cell operating voltage ( $V_{\mathrm {MIN}})$ for a 6T SRAM high-density cell design.

Yi-Ting Wu

Papers

Simulation-Based Study of Hybrid Fin/Planar LDMOS Design for FinFET-Based System-on-Chip Technology

Simulation-Based Study of High-Density SRAM Voltage Scaling Enabled by Inserted-Oxide FinFET Technology

Photoanode Modified by PbTiO3 or PbTiO3/TiO2 Nanofibers in Dye-Sensitized Solar Cell

UV Enhanced Field Emission for β-Ga 2 O 3 Nanowires

Cell Ratio Tuning for High-Density SRAM Voltage Scaling With Inserted-Oxide FinFETs