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This paper investigates the impact of an atomic layer-deposited Y2O3 dielectric on the passivation of a GeO2 layer in GeO2-based Ge gate stacks. The equivalent oxide thickness scalability and thermal stability of the ultrathin Y2O3 layer are evaluated at different Y2O3 thicknesses and annealing conditions in detail. Experimental results show that a Y2O3 layer thickness of 1.0 nm is required to serve as a GeO2 passivation layer while retaining gate-stack performance at 400 °C postdeposition annealing. However, at a higher annealing temperature of 500 °C, the barrier property deteriorates and allows GeO desorption. The proposed gate-stack implies the applicability of a Y2O3 passivation method for further scaled GeO2-based Ge gate stacks. [ABSTRACT FROM PUBLISHER]

AlGaN/GaN high-electron-mobility transistors (HEMT) have been grown by radio frequency molecular beam epi-taxy (RF-MBE) on 3″ Si substrates. A record low contact resistance Rc ˜ 0.11 Ω.mm has been achieved for GaN HEMTs on Si by using non alloyed ohmic contacts regrown by MBE. Owing to the low contact resistance a 75-nm gate length unpassivated HEMT shows intrinsic current gain cut-off frequency fT =153 GHz, a high saturation drain current density> 1.3 A/mm and a low RON of 1 Ω.mm, among the best reported for HEMTs on Si. With further scaling GaN HEMTs on Si can compete in the high-performance RF arena with similar devices on SiC, while exploiting the many advantages of integration with Si. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

A fast-response colorimetric ultraviolet-C (UVC) sensor was demonstrated using a gallium oxide (Ga2O3) photocatalyst with small amounts of triethanolamine (TEOA) in methylene blue (MB) solutions and a conventional RGB photodetector. The color of the MB solution changed upon UVC exposure, which was observed using an in situ RGB photodetector. Thereby, the UVC exposure was numerically quantified as an MB reduction rate with the R value of the photodetector, which was linearly correlated with the measured spectral absorbance using a UV-Vis spectrophotometer. Small amount of TEOA in the MB solution served as a hole scavenger, which resulted in fast MB color changes due to the enhanced charge separation. However, excessive TEOA over 5 wt.% started to block the catalytical active site on the surface of Ga2O3, prohibiting the chemical reaction between the MB molecules and catalytic sites. The proposed colorimetric UVC sensor could monitor the detrimental UVC radiation with high responsivity at a low cost. [ABSTRACT FROM AUTHOR]

Graphene nanoribbons are a greatly intriguing form of nanomaterials owing to their unique properties that overcome the limitations associated with a zero bandgap of two-dimensional graphene at room temperature. Thus, the fabrication of graphene nanoribbons has garnered much attention for building high-performance field-effect transistors. Consequently, various methodologies reported previously have brought significant progress in the development of highly ordered graphene nanoribbons. Nonetheless, easy control in spatial arrangement and alignment of graphene nanoribbons on a large scale is still limited. In this study, we explored a facile, yet effective method for the fabrication of graphene nanoribbons by employing orientationally controlled electrospun polymeric nanowire etch-mask. We started with a thermal chemical vapor deposition process to prepare graphene monolayer, which was conveniently transferred onto a receiving substrate for electrospun polymer nanowires. The polymeric nanowires act as a robust etching barrier underlying graphene sheets to harvest arrays of the graphene nanoribbons. On varying the parametric control in the process, the size, morphology, and width of electrospun polymer nanowires were easily manipulated. Upon O2 plasma etching, highly aligned arrays of graphene nanoribbons were produced, and the sacrificial polymeric nanowires were completely removed. The graphene nanoribbons were used to implement field-effect transistors in a bottom-gated configuration. Such approaches could realistically yield a relatively improved current on–off ratio of ~30 higher than those associated with the usual micro-ribbon strategy, with the clear potential to realize reproducible high-performance devices. [ABSTRACT FROM AUTHOR]

Record high on-current of 78 \mu\A/\mu\m in a tunnel field-effect transistor (TFET) is achieved at 0.5 V at room temperature. The TFET employs a staggered AlGaSb/InAs heterojunction with the tunneling direction oriented in-line with the gate field. The measured results are consistent with numerical simulation of the device structure. Simulations of optimized structures suggest that switching speed comparable to that of the MOSFET should be achievable with improvements in the source and drain resistances. [ABSTRACT FROM AUTHOR]

This study explores the potential of 700‐nm‐thick heteroepitaxial α‐Ga2O3 thin films on c‐plane sapphire substrates for X‐ray detector applications. The crystal quality and optical bandgap of the heteroepitaxial α‐Ga2O3 thin films are comparable to those of high‐quality α‐Ga2O3 thin films. The α‐Ga2O3 thin film X‐ray detector with a metal–semiconductor–metal structure exhibits a charge neutral point shift, resulting in a short‐circuit current density of 9.07 nA cm−2 and an open‐circuit voltage of –1.2 V. The detector achieves the highest signal‐to‐noise ratio of 973 at 0 V, while the maximum sensitivity (14.7 μC Gyair−1 cm−2) occurs at 10 V. The proposed X‐ray detector demonstrates a reliable transient response and long‐term robustness, suggesting the promise of heteroepitaxial α‐Ga2O3 for low‐cost, high‐quality, large‐area X‐ray detectors. [ABSTRACT FROM AUTHOR]

MoTe 2 is the least explored material in the Molybdenum-chalcogen family. Molecular beam epitaxy (MBE) provides a unique opportunity to tackle the small electronegativity difference between Mo and Te while growing layer by layer away from thermodynamic equilibrium. We find that for a few-layer MoTe 2 grown at a moderate rate of ∼6 min per monolayer, a narrow window in temperature (above Te cell temperature) and Te:Mo ratio exists, where we can obtain pure phase 2 H -MoTe 2 . This is confirmed using reflection high-energy electron diffraction (RHEED), Raman spectroscopy and X-ray photoemission spectroscopy (XPS). For growth on CaF 2 , Grazing incidence X-ray diffraction (GI-XRD) reveals a grain size of ∼90 Å and presence of twinned grains. In this work, we hypothesis the presence of excess Te incorporation in MBE grown few layer 2 H -MoTe 2 . For film on CaF 2 , it is based on >2 Te:Mo stoichiometry using XPS as well as ‘a’ and ‘c’ lattice spacing greater than bulk 2 H -MoTe 2 . On GaAs, its based on observations of Te crystallite formation on film surface, 2 × 2 superstructure observed in RHEED and low energy electron diffraction, larger than bulk c-lattice spacing as well as the lack of electrical conductivity modulation by field effect. Finally, thermal stability and air sensitivity of MBE 2H-MoTe 2 is investigated by temperature dependent XRD and XPS, respectively. [ABSTRACT FROM AUTHOR]

The use of a GeO 2 interfacial layer (IL) between a high-k dielectric and a Ge substrate helps to reduce the interface state density in Ge MOS devices. We report that the presence of the GeO 2 IL changes the effective work function (eWF) of the gate stack when annealed after high-k dielectric deposition. The eWF is reduced from 4.31 eV to 3.98 eV for TaN and from 5.00 eV to 4.44 eV for Ni. Consequently, the threshold voltage ( V th ) decreases from 0.69 V to 0.21 V for Ni after post deposition annealing. Our investigation confirms that the generation of oxygen vacancies in the GeO 2 IL near the Ge substrate is the main cause of the eWF modulation. In addition, the reliability of the GeO 2 IL is investigated via the conductance method and a constant-current stress test. [ABSTRACT FROM AUTHOR]

Al and In dopants are codoped in β -Ga 2 O 3 nanostructures via hydrothermal synthesis. Unlike single-dopant β -Ga 2 O 3 nanostructures, less mechanical strain is induced in the β -Ga 2 O 3 nanostructures with the codoping of Al and In atoms. This is attributed to the size compensation effect. The induced mechanical strain caused by each dopant in the β -Ga 2 O 3 nanostructures is analyzed using X-ray diffraction. Chemical states are also compared after Al and In doping in the β -Ga 2 O 3 nanostructures. Finally, the photocatalytic properties of various β -Ga 2 O 3 nanostructures at different Al and In concentrations are compared via the decomposition of methylene blue from UVC irradiation with a wavelength of 254 nm. Compared to the single-dopant β -Ga 2 O 3 nanostructures, enhanced photocatalytic activity is obtained with higher dopant concentrations when Al and In atoms are codoped in the β -Ga 2 O 3 nanostructures. This codoping technique could be applied to various applications where higher doping concentrations are advantageous while minimizing the induced lattice deformation of the β -Ga 2 O 3. [Display omitted] • Al dopants induce compressive strain in β -Ga 2 O 3 nanostructures. • In dopants induce tensile strain in β -Ga 2 O 3 nanostructures. • Nearly strain-free structure forms via codoping of Al and In atoms. • Enhanced photocatalytic activity is obtained with codoping of Al and In atoms. [ABSTRACT FROM AUTHOR]

The reversible photoinduced wettability of β-Ga 2 O 3 thin films with different film thicknesses is investigated under ultraviolet C irradiation, and the results are compared with those from an amorphous SiO 2 surface. The Ga 2 O 3 surface exhibits reversible photoinduced wettability under ultraviolet-C (UVC) radiation centered at 254 nm. The critical transition time (CTT) of the 50-nm thick β-Ga 2 O 3 film is comparable to that of the 8-nm thick β -Ga 2 O 3 film, but the CTT value increases significantly for the 100-nm thick β -Ga 2 O 3 film. The thickness-dependent reversible wettability in the Ga 2 O 3 surface is explained using a penetration-diffusion model. The photoinduced Ga 2 O 3 surface also exhibits substantial antimicrobial activity in Escherichia coli cells. The experimental findings in this work indicate that Ga 2 O 3 can be used in various applications, including self-cleaning, anti-fogging, and antimicrobial activities. • The surface of Ga 2 O 3 is activated under ultraviolet-C irradiation. • The rate of photoinduced wettability changes depending on Ga 2 O 3 thickness. • The photoinduced Ga 2 O 3 surface exhibits antibacterial activity. [ABSTRACT FROM AUTHOR]

The quality of the dielectric/organic semiconductor interface is a critical issue, because it determines the charge transport properties in organic thin-film transistors (OTFTs). High- k organic-inorganic hybrid films have received considerable attention for their outstanding dielectric properties, including low leakage currents, high breakdown fields, and suitable band offsets against the organic semiconductor. However, Hf and Zr hybrid gate dielectrics on p-type OTFTs show poor charge transport properties in the organic semiconductor channel, due to the polaron disorder elicited by the high- k properties and the presence of the –N(CH 3) 2 polarity (hole trapper) on the dielectric/semiconductor interface. In this report, the surface of the Hf and Zr hybrid dielectrics was capped by an ultra-thin poly-1,3,5-trivinyl-1,3,5,-trimethyl-cyclosiloxane (pV3D3) layer formed via an initiated chemical vapor deposition (iCVD) process, to modify the hybrid dielectrics/semiconductor interface. The pV3D3-capped Hf and Zr hybrid OTFTs show an enhanced V T stability while a large amount of V T shift was observed from the Hf and Zr hybrid OTFTs. This large amount of V T shift is attributed to the hole trap sites originated by –N(CH 3) 2 on the uncapped hybrid dielectrics. Furthermore, the p-type OTFTs with the pV3D3-capped hybrid dielectrics show a higher mobility than those with the uncapped hybrid dielectrics. The presence of the non-polar/low- k pV3D3 on the hybrids contribute to narrow the density of state (DOS) in the organic channel, improving the charge transport properties. This combined approach using the bulk layer of Hf and Zr hybrid films and the pV3D3 capping layer can overcome the limitations of single-layer hybrid dielectrics and improve the overall device performance of the OTFTs. [Display omitted] • Performance Enhancement of p-type OTFTs through simple surface modification. • Ultra-thin (~1 nm) non-polar low-k dielectric on the hybrid. • Simple process to change the surface properties. • Systematic investigation of interface quality which affect charge transport in organic semiconductor. [ABSTRACT FROM AUTHOR]

• The residual F in the CVD W was diffused into Al 2 O 3 , Si 3 N 4 , SiO 2 , and the interface at SiO 2 /poly-Si after the subsequent annealing process at 900 °C for 1 s. • The diffused F increased the SiO 2 thickness and altered the charge-trap density in the Al 2 O 3 , Si 3 N 4 , SiO 2 , and SiO 2 /poly-Si interface. • The memory window and program/erase retention properties degraded while the charge-transport and endurance characteristics improved with the CVD W memory as compared to the PVD W memory. A charge-trap flash (CTF) memory stack of chemical vapor deposition (CVD) tungsten (W) was systematically compared with a physical vapor deposited (PVD) W memory stack. The residual F in the CVD W was diffused into Al 2 O 3 , Si 3 N 4 , SiO 2 , and the interface at SiO 2 /poly-Si after the subsequent annealing process at 900 °C for 1 s. The diffused F increased the SiO 2 thickness and altered the charge-trap density in the Al 2 O 3 , Si 3 N 4 , SiO 2 , and SiO 2 /poly-Si interface, and this eventually affected memory performance and reliability. The memory window and program/erase retention properties degraded while the charge-transport and endurance characteristics improved with the CVD W memory as compared to the PVD W memory. [ABSTRACT FROM AUTHOR]

Gallium oxide (Ga 2 O 3 ) is attracting attention as a next-generation semiconductor material for power device because it has a wide energy band gap and high breakdown electric field. We deposited a Sn polymer, poly-tetraallyl tin, on Ga 2 O 3 samples using a disclosed initiated chemical vapor deposition (iCVD) process. The Sn dopant of the Sn polymer layer is injected into the Ga 2 O 3 through a heat treatment process. Diffusion model of Sn into the Ga 2 O 3 is proposed through secondary ion mass spectroscopy analysis and bond dissociation energy. The fabricated device exhibited typical n-type field-effect transistor (FET) behavior. Ga 2 O 3 Sn-doping technology using iCVD will be applied to 3D structures and trench structures in the future, opening up many possibilities in the Ga 2 O 3 -based power semiconductor device manufacturing process., (© 2024 IOP Publishing Ltd.)

A liquid Ga-based synaptic device with two-terminal electrodes is demonstrated in NaOH solutions at 50 °C. The proposed electrochemical redox device using the liquid Ga electrode in the NaOH solution can emulate various biological synapses that require different decay constants. The device exhibits a wide range of current decay times from 60 to 320 ms at different NaOH mole concentrations from 0.2 to 1.6 M. This research marks a step forward in the development of flexible and biocompatible neuromorphic devices that can be utilized for a range of applications where different synaptic strengths are required lasting from a few milliseconds to seconds., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)