High photoresponsivity MoS2phototransistor through enhanced hole trapping HfO2gate dielectric.

Phototransistor using 2D semiconductor as the channel material has shown promising potential for high sensitivity photo detection. The high photoresponsivity is often attributed to the photogating effect, where photo excited holes are trapped at the gate dielectric interface that provides additional gate electric field to enhance channel charge carrier density. Gate dielectric material and its deposition processing conditions can have great effect on the interface states. Here, we use HfO2gate dielectric with proper thermal annealing to demonstrate a high photoresponsivity MoS2phototransistor. When HfO2is annealed in H2atmosphere, the photoresponsivity is enhanced by an order of magnitude as compared with that of a phototransistor using HfO2without annealing or annealed in Ar atmosphere. The enhancement is attributed to the hole trapping states introduced at HfO2interface through H2annealing process, which greatly enhances photogating effect. The phototransistor exhibits a very large photoresponsivity of 1.1 × 107A W-1and photogain of 3.3 × 107under low light illumination intensity. This study provides a processing technique to fabricate highly sensitive phototransistor for low optical power detection.

Improving Performance and Breakdown Voltage in Normally-Off GaN Recessed Gate MIS-HEMTs Using Atomic Layer Etching and Gate Field Plate for High-Power Device Applications.

A typical method for normally-off operation, the metal-insulator-semiconductor-high electron mobility transistor (MIS-HEMT) has been investigated. Among various approaches, gate recessed MIS-HEMT have demonstrated a high gate voltage sweep and low leakage current characteristics. Despite their high performance, obtaining low-damage techniques in gate recess processing has so far proven too challenging. In this letter, we demonstrate a high current density and high breakdown down voltage of a MIS-HEMT with a recessed gate by the low damage gate recessed etching of atomic layer etching (ALE) technology. After the remaining 3.7 nm of the AlGaN recessed gate was formed, the surface roughness (Ra of 0.40 nm) was almost the same as the surface without ALE (no etching) as measured by atomic force microscopy (AFM). Furthermore, the devices demonstrate state-of-the-art characteristics with a competitive maximum drain current of 608 mA/mm at a VG of 6 V and a threshold voltage of +2.0 V. The devices also show an on/off current ratio of 109 and an off-state hard breakdown voltage of 1190 V. The low damage of ALE technology was introduced into the MIS-HEMT with the recessed gate, which effectively reduced trapping states at the interface to obtain the low on-resistance (Ron) of 6.8 Ω·mm and high breakdown voltage performance.

A Brief Overview of the Rapid Progress and Proposed Improvements in Gallium Nitride Epitaxy and Process for Third-Generation Semiconductors with Wide Bandgap.

In this paper, we will discuss the rapid progress of third-generation semiconductors with wide bandgap, with a special focus on the gallium nitride (GaN) on silicon (Si). This architecture has high mass-production potential due to its low cost, larger size, and compatibility with CMOS-fab processes. As a result, several improvements have been proposed in terms of epitaxy structure and high electron mobility transistor (HEMT) process, particularly in the enhancement mode (E-mode). IMEC has made significant strides using a 200 mm 8-inch Qromis Substrate Technology (QST®) substrate for breakdown voltage to achieve 650 V in 2020, which was further improved to 1200 V by superlattice and carbon-doped in 2022. In 2016, IMEC adopted VEECO metal-organic chemical vapor deposition (MOCVD) for GaN on Si HEMT epitaxy structure and the process by implementing a three-layer field plate to improve dynamic on-resistance (RON). In 2019, Panasonic HD-GITs plus field version was utilized to effectively improve dynamic RON. Both reliability and dynamic RON have been enhanced by these improvements.

Highly Active NiO-Ni(OH)2 -Cr2 O3 /Ni Hydrogen Evolution Electrocatalyst through Synergistic Reaction Kinetics.

High activity catalysts for hydrogen evolution reaction (HER) play a key role in converting renewable electricity to storable hydrogen fuel. Great effort has been devoted to the search for noble metal free catalysts to make electrolysis viable for practical applications. Here, a non-precious metal oxide/metal catalyst with high intrinsic activity comparable to Pt/C was reported. The electrocatalyst consisting of NiO, Ni(OH)2 , Cr2 O3 , and Ni metal exhibits a low overpotential of 27, 103, and 153 mV at current densities of 10, 100, and 200 mA cm-2 , respectively, in a 1.0 m NaOH electrolyte. The activity is much higher than that of NiOx /Ni or Cr2 O3 alone, showing the synergistic effect of NiOx /Ni and Cr2 O3 on catalyzing HER. Density functional theory calculations shows that NiO and Cr2 O3 on Ni surface lower the disassociation energy barrier for breaking H-OH bond, while Ni(OH)2 and Cr2 O3 create preferred sites on Ni surface with near-zero H* adsorption free energy to promote H* to gaseous H2 evolution. These synergistic effects of multiple-oxides/metal composition enhance the disassociation of H-OH and the evolution of H* to gaseous H2 , thus achieving high activity and demonstrating a promising composition design for noble metal free catalyst.

Development of GaN HEMTs Fabricated on Silicon, Silicon-on-Insulator, and Engineered Substrates and the Heterogeneous Integration.

GaN HEMT has attracted a lot of attention in recent years owing to its wide applications from the high-frequency power amplifier to the high voltage devices used in power electronic systems. Development of GaN HEMT on Si-based substrate is currently the main focus of the industry to reduce the cost as well as to integrate GaN with Si-based components. However, the direct growth of GaN on Si has the challenge of high defect density that compromises the performance, reliability, and yield. Defects are typically nucleated at the GaN/Si heterointerface due to both lattice and thermal mismatches between GaN and Si. In this article, we will review the current status of GaN on Si in terms of epitaxy and device performances in high frequency and high-power applications. Recently, different substrate structures including silicon-on-insulator (SOI) and engineered poly-AlN (QST®) are introduced to enhance the epitaxy quality by reducing the mismatches. We will discuss the development and potential benefit of these novel substrates. Moreover, SOI may provide a path to enable the integration of GaN with Si CMOS. Finally, the recent development of 3D hetero-integration technology to combine GaN technology and CMOS is also illustrated.

Tetrazolium Salt WST-8 as a Novel and Reliable Chromogenic Indicator for the Assessment of Boar Semen Quality.

A tetrazolium salt, 2-[2-methoxy-4-nitrophenyl]-3-[4-nitrophenyl]-5-[2,4-disulfophenyl]-2H-tetrazolium (WST-8), has been used widely to determine cell viability; however, its application in the field of reproduction is still limited due to this assay merely providing information regarding cell viability. The aim of this study was to correlate the WST-8 reduction rate with various sperm quality-related parameters (i.e., sperm viability, motility, progressive motility, acrosome integrity and mitochondria integrity) in order to provide a rapid, reliable and affordable assessment for boar semen quality evaluation. Using different ratios of active/damaged sperm cells, we first validated our sample preparations by standard flow cytometry and computer-assisted sperm analysis. Further analyses demonstrated that the most efficient experimental condition for obtaining a reliable prediction model was when sperm concentration reached 300 × 106 cells/mL with the semen/cell-counting kit-8 (CCK-8®) ratio of 200/10 and incubated time of 20 min. Under this set up, the WST-8 reduction rate (differences on optic density reading value, ΔOD at 450 nm) and sperm parameters were highly correlated (p < 0.01) for all sperm parameters evaluated. In the case of limited semen samples, a minimal semen concentration at 150 × 106 cells/mL with the semen/CCK-8® ratio of 200/20 and incubation time for 30 min could still provide reliable prediction of sperm parameters using the WST-8 assay. Our data provide strong evidence for the first time that the WST-8 assay could be used to evaluate boar semen quality with great potential to be applied to different mammalian species.

Dependence of Photoresponsivity and On/Off Ratio on Quantum Dot Density in Quantum Dot Sensitized MoS2 Photodetector.

Non-radiative energy transfer (NRET) from quantum dots (QDs) to monolayer MoS2 has been shown to greatly enhance the photoresponsivity of the MoS2 photodetector, lifting the limitations imposed by monolayer absorption thickness. Studies were often performed on a photodetector with a channel length of only a few µm and an active area of a few µm2. Here, we demonstrate a QD sensitized monolayer MoS2 photodetector with a large channel length of 40 µm and an active area of 0.13 mm2. The QD sensitizing coating greatly enhances photoresponsivity by 14-fold at 1.3 µW illumination power, as compared with a plain monolayer MoS2 photodetector without QD coating. The photoresponsivity enhancement increases as QD coating density increases. However, QD coating also causes dark current to increase due to charge doping from QD on MoS2. At low QD density, the increase of photocurrent is much larger than the increase of dark current, resulting in a significant enhancement of the signal on/off ratio. As QD density increases, the increase of photocurrent becomes slower than the increase of dark current. As a result, photoresponsivity increases, but the on/off ratio decreases. This inverse dependence on QD density is an important factor to consider in the QD sensitized photodetector design.

Genetic correlations between male reproductive traits and growth traits in growth performance tested Duroc, Landrace and Yorkshire breed boars.

Male-related traits at 180-225 days of age for 6464 grow-finish performance tested boars were measured from 2000 to 2016. Heritability estimates and genetic correlations among average daily gain, feed efficiency, back fat thickness, teat counts, mounting libido, leg locomotion, penile length, sperm motility, sperm concentration and total sperm counts were estimated by VCE software using a multiple traits animal model in each breed. Growth-tested boars had heritability estimates of male reproductive traits in 0.34-0.56 of teat counts, 0.12-0.20 of libido, 0.08-0.12 of locomotion, 0.17-0.58 of penile length, 0.04-0.21 of sperm motility and concentration, 0.17-0.30 of total sperm counts. Total sperm counts were genetically positively correlated with penile length in all breeds. Boars with higher total sperm counts had genetically better libido and locomotion. Genetic correlation between feed efficiency and sperm motility and feed efficiency and sperm concentration were positive in Duroc and negative in Landrace and Yorkshire. Sperm motility and concentration were genetically negatively correlated with average daily gain in Yorkshire. Male reproductive traits of imported breeds could be improved with care in the change of growth traits, especially in Yorkshire.

Antagonistic activity against Salmonella infection in vitro and in vivo for two Lactobacillus strains from swine and poultry.

In this study, we isolated two lactobacillus strains, i.e., strain LAP5 and LF33, from swine and poultry, respectively, and showed that both strains were acid as well as bile tolerant and were able to adhere to the cultured human intestinal cell lines, such as Int-407 and Caco-2 cells, and to the intestinal epithelium cells isolated from swine, poultry and mouse (BALB/c). Both of these LAB strains were shown to inhibit the growth of Escherichia coli, Salmonella typhimurium, Staphylococcus aureus and Bacillus cereus. When these two LAB strains were evaluated for their antagonistic activity against Salmonella (S. typhimurium) invasion to cultured human intestinal cell line Int-407 and to mouse (BALB/c) liver and spleen, these two LAB strains were found to have significant antagonistic effect.