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Abstract-Type-II n-p-n InP/GaAsSb/InP double heterostructure bipolar transistors (DHBTs) that are fabricated by optical lithography with a 0.6 × 5 μm² emitter on a 20-nm compositionally uniform GaAszSb1-x carbon-doped base with x = 0.60 and a 75-nm InP collector show current-gain cutoff frequencies as high as 423 GHz at 10 mA/μm2 and feature a BVCEO = 4 V. The pseudomorphic As-rich InP/GaAsSb DHBTs feature a high maximum dc current gain of > 160, owing to the reduction of the type-II conduction band discontinuity ΔEc and the associated recombination at the InP/GaAsSb emitter-base interface. This brief demonstrates that the InP/GaAsSb DHBT technology can combine high gain, wide bandwidths, high-current drivability, and structural simplicity. [ABSTRACT FROM AUTHOR]

Transition metal cobalt-doped zinc oxide (ZnO) nanorods with room-temperature ferromagnetism have been rationally fabricated by a facile solution-based route. The synthesis just involves hydrolyses and condensation processes, which allow the growth of transition metal-doped ZnO nanostructures at a high yield, low cost, and mild temperatures. The morphology of the products can be controlled by tuning the reaction conditions such as precursors, solvents, and reaction time. The nanorods show room-temperature ferromagnetic behavior using C20H37NaO7S as a surfactant. The origin of the ferromagnetism is also discussed. [ABSTRACT FROM AUTHOR]

In this work, thermal atomic layer deposition (ALD) of HfO2 on monolayer (ML) MoS2 with 1 nm Al2O3 seed layer by e-beam evaporation was explored. With the 1 nm Al2O3 seed layer, a uniform HfO2 layer can be deposited on the ML MoS2 with bare influence on the ML MoS2 structure. After coating a uniform HfO2, abundant electrons are accumulated in MoS2 and SiO2 resulting in a high on/off current ratio of ~109 and a dramatic reduction of subthreshold swing (SS) from 1943 to 168 mV/dec of back-gated ML MoS2 transistor on 300 nm SiO2. A low SS of 103 mV/dec was further obtained from top-gated transistor with ~23.3 nm HfO2 as the gate oxide. The results manifest the beneficial influence of using 1 nm Al2O3 on the electrical performance of ML MoS2 transistors, suggesting a feasible strategy for ALD of high-k dielectric layer on ML 2D materials. [ABSTRACT FROM AUTHOR]

Various surface treatment methods have been previously applied on the GaN high electron mobility transistor (HEMT). In this study, the effects of N2O surface treatment on the electrical properties of InAlN/GaN HEMT were studied. With this surface treatment, the ideality factor of the gate Schottky barrier diode decreases from 7.70 to 1.30, and the barrier height of SBD increases from 0.508 eV to 1.053 eV (~two folds), an indication of the improved Schottky contact characteristic. Negative-shifted threshold voltage, decreased gate capacitance and two-dimensional electron gas (2DEG) electron density were observed. Both the intrinsic transconductance and 2DEG electron mobility are improved. The 2DEG electron mobilities limited by various scattering mechanisms are extracted using two-dimensional (2D) scattering theory. It is found that N2O surface treatment results in the increase of the 2DEG electron mobility due to the weakened polar optical phonon, interface roughness, and polarization Coulomb field scatterings. This study offers a feasible way to further enhance InAlN/GaN HEMT performances by using N2O surface treatment. [ABSTRACT FROM AUTHOR]

In this letter, we present the electrical properties of the InAlN/GaN metal–insulator–semiconductor high-electron-mobility transistor (MISHEMT) with plasma enhanced atomic layer-deposited ZrO2 as the gate dielectric. The InAlN/GaN MISHEMT with an on/off current (Ion/Ioff) ratio of 1.46 × 109 as well as a subthreshold swing of 85 mV/dec was achieved. The interface trap density (Dit) decreased from 1.16 × 1012 eV−1 cm−2 (at EC − ET = 0.26 eV) to 4.68 × 1011 eV−1 cm−2 (at EC − ET = 0.40 eV), indicating a good interface property. This study suggests a feasible way for the application of ZrO2/InAlN/GaN MISHEMTs. [ABSTRACT FROM AUTHOR]

We demonstrate staggered ("type-II") lineup lattice-matched GaAs0.51Sb0.49-InP unitraveling carrier photodiodes (UTC-PDs) for application near 1.55 μm. The GaAsSb absorbing layer conduction band edge lines up ΔEC=0.11 eV above that of InP, and hence, allows the direct injection of photogenerated electrons into an InP collector-without any need for compositional grading around the GaAsSb-InP interface-thus simplifying epitaxial growth and device fabrication. InP-GaAsSb UTC-PDs show low dark current levels, and measurable bandwidths are limited by the test equipment. A transit-limited bandwidth of 105 GHz for a PD with a 1000-GaAsSb absorption layer (C:5×1018/cm3) and a 2000 InP collector is inferred from the variation of photoresponse bandwidth with device area. [ABSTRACT FROM PUBLISHER]

In this work, three-dimensional (3D) Ge condensation was carried out to explore the merits of Ge condensation method in fabricating low-dimensional SiGe-on-insulator (SGOI) and Ge-on-insulator (GOI) structures. Through varying the width of SGOI wires from 220 nm to 50 μm before Ge condensation, the Ge content of SiGe wires can be easily modulated from 1.0 to 0.55 after 3D Ge condensation facilitating fabrication of SiGe/Ge heterojunction nanowires (NWs). Based on the volume change of Si, Ge and SiO2 with consideration of a geometry factor, a simple 3D Ge condensation model was built. It is found that the enrichment of Ge content mainly comes from condensation effect along directions with small dimensions. The proposed 3D condensation model can be a guidance to design and fabricate low-dimensional SGOI, GOI and even SiGe/Ge heterostructures on insulator materials. [ABSTRACT FROM AUTHOR]

The effect of the negative substrate bias (Vsub) on the device performance of the InAlN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) is studied. When the Vsub decreased from 0 V to  −40 V, the two-dimensional electron gas (2DEG) electron density (n2D) under the gate region decreased, while the 2DEG electron mobility (µ2DEG) under the gate region was significantly improved. Due to the InGaN back barrier layer and the thin GaN channel layer (15 nm), the 2DEG electrons in the channel are injected into the InGaN back barrier layer with negative Vsub, leading to the decreased n2D. The decrease of the n2D caused the decrease of the collision probability between the polar optical phonon (POP) and the 2DEG electrons, and the enlarged distance between the 2DEG electrons and the AlN/GaN interface, resulting in the weaker POP and interface roughness scatterings and higher µ2DEG. This provides a possible way to increase 2DEG electron mobility and further improve the device performance of InAlN/GaN MIS-HEMTs. [ABSTRACT FROM AUTHOR]

We report an 80 nm gate-length In0.17Al0.83N/GaN high-electron mobility transistor (HEMT) on silicon substrate with a record low gate leakage current of 7.12 × 10−7 A mm−1, a record high on/off current ratio of 1.58 × 106, and a steep subthreshold swing of 65 mV dec−1, which are excellent features among the reported InAlN/GaN HEMTs on Si. Due to the excellent DC performance, a current gain cutoff frequency fT of 200 GHz is achieved, resulting in fT × Lg = 16 GHz μm for GaN HEMTs on Si which to the best of our knowledge is a new record. [ABSTRACT FROM AUTHOR]

We reported high performance anatase-TiO2 thin film transistors with a two-step oxidized TiO2 channel (O2 annealing and N2O plasma treatment) and O2 plasma enhanced atomic layer-deposited ZrO2 gate dielectric. The transistors using 60 nm TiO2 as the active channel exhibited a steep subthreshold swing of 112 mV dec−1 and a high on/off current ratio of 1.4 × 108. The superior performances, achieved by the two-step oxidizing process and the utilization of ZrO2 as the high-k gate dielectric, show their great potential to be applied in future electronic and optical systems, such as active-matrix displays and ultraviolet sensors. [ABSTRACT FROM AUTHOR]

Porous Si3N4 ceramics were fabricated through a gelcasting method followed by pressureless sintering at 1680 °C. Water-soluble copolymer of isobuthylene and maleic anhydrade (Isobam) was used as both dispersant and gelling agent, the Si3N4 slurry with 0.2 wt% Isobam was favorable to form a fine homogeneous green body. As the solid loading increased from 25 to 40 vol%, porous Si3N4 ceramics with high porosity of 50-56% and high flexural strength of 167-119 MPa were obtained. This was attributed to fine β-Si3N4 grains and some large elongated grains with interlocking microstructure. [ABSTRACT FROM AUTHOR]