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A high performance (001) $\beta$ -Ga 2 O 3 vertical Schottky barrier diode (SBD) with double step structure termination using thermally oxided TiO x dielectrics is reported in this paper. The novel termination effectively reduces the leakage current caused by the high electric field at the edge of Schottky junction. By using the double step structure TiO x layers, the breakdown voltage $(V_{\text{br}})$ increases from 460V to 950V, and the specific on-resistance $(R_{\text{on},\text{sp}})$ just increases from 2.7 $\mathrm{m}\Omega\cdot \text{cm}^{3}$ to 2.8 $\mathrm{m}\Omega\cdot \text{cm}^{2}$ . The fabricated device shows a high power figure of merit (PFOM) of 329 MW/cm2. These results show a new way to improve the breakdown characteristics of $\beta$ -Ga 2 O 3 SBD.

In this paper, the gate leakage and deep-level trapping effect in thin-barrier InAIN/GaN high-electron-mobility transistors (HEMTs) are investigated based on multiple characterization methods such as DC measurement, pulsed current-voltage measurement, capacitance measurement and frequency-dependent conductance method. In addition, the Schottky gate barrier height and ideality factor as well as the trap density under the gate are extracted. The results show that the current hysteresis and current collapse of our samples are mainly induced by the trapping effect with hot-carrier injection rather than the gate-leakage injection mechanism, which indicates that the reduction of gate leakage can improve the DC characteristics but not the dynamic performance.

In this paper, high-performance 1×128 linear arrays of 4H-SiC ultraviolet (UV) avalanche photodiode (APD) with dual-frequency plasma enhanced chemical vapor deposition (PECVD) passivation are demonstrated for the first time. The results show that SiNx dielectric deposited by dual-frequency PECVD can effectively reduce the leakage current at high bias voltages. Due to the improved 4H-SiC epi-layer material and SiNx passivation, the fabricated 22 mm-long 1×128 4H-SiC APD linear arrays exhibit an excellent performance with a high pixel yield of 100% and a small breakdown voltage variation of 0.2 V, which is the best result ever reported. At room temperature, the pixels have a gain of over 10

In the natural disaster, the communication infrastructure is damaged and cannot communicate, the rescue team's action is blocked, and the relief work will face severe challenges. However, due to the precipitous terrain in some areas, emergency communication vehicles can not arrive in time to provide communication services, which delays the best time for rescue operations. The UAV has a very good mobility, relatively speaking, the range of action will not be limited by the geographical environment, and easy to deploy, can provide timely communication services for this emergency. In this paper, a mobile relay aviation base station model is established to provide fast and reliable communication for disaster areas. In this model, the location of base station is fixed and the location of mobile relay is variable. The system throughput is optimized by optimizing the height of mobile relay. The above optimization problem is a non deterministic polynomial problem, which is solved by the improved particle swarm optimization algorithm. In this scenario, the fading model uses a free-space propagation loss model.

In this letter, an avalanche photodiode (APD) for ultraviolet detection was fabricated on a 4H-SiC epi-layer with a radius of 150 µm. By adopting passive quenching method, the impact of quenching resistor on single photon detection performance of the fabricated APD was investigated for the first time. It is found that both dark count rate (DCR) and single photon detect efficiency (SPDE) were reduced with the increasing quenching resistance. When the DCR fixed at 5 Hz/μm2 , the SPDE is 7.1% /6.7%/5.4%/5.2% corresponding to the quenching resistance of 10/20/50/100 kΩ. Variation of the SPDEs can be ascribed to the changing death time by comparing the photon counting spectra with various resistors. The obtained results have built up a good basis for the design of SiC APD single photon detection.

This paper introduces a high performance indoor location method based on random forest. Firstly, the access point with poor signal strength and unstable signal is deleted through the signal strength of the access point. Then the information gain method is used to select the access points with better positioning effect from the remaining access points to form the access points set and establish the location fingerprint database. Then, all positions in the location scene are grouped by clustering algorithm, and then a random forest model is built for each position. The location process USES the random forest model to determine the user location. The experimental results show that by constructing a high precision and high stability stochastic forest model, this paper can effectively solve the problem of limited positioning accuracy, unstable positioning effect and easy to fall into overfitting of the single-decision tree model, and improve the positioning stability and positioning accuracy. The average error of the indoor positioning method mentioned in this paper is at least 1.3718m, and the variance of the positioning result is calculated on this basis, which is 0.0173 in this paper.

Graphene directly grown on an 4H-SiC (0 0 0 1) substrate by chemical vapor deposition was studied: it was shown that Si evaporation process is not completely halted during graphene growth when TG ≥ 1400 °C, the SiC substrate decomposes at the position of graphene coverage. AFM and Raman spectrum results reveal that carbon concentration significantly influences graphene growth rate and morphology/structure. It is found that the quality of graphene film depends on the growth temperature and the flow of carbon source. We develop a new gradient growth method to produce a feasible graphene material for electronic devices. Graphene grown by this method has a flat-morphology structure, low wrinkle density, high crystal quality, good uniformity, and outstanding electrical transport properties. Nitrogen doping has an n-type doping effect on graphene carrier concentration. The main component of nitrogen-bond type is the graphitic configuration. The graphene material with nitrogen doping reaches a record mobility of 9010 cm2/V·s by room temperature Hall effect measurement, indicating graphene grown by gradient method with suitable nitrogen doping could yield a high quality film comparable to that by traditional method.

In this paper, we report on a novel enhancement-mode AlGaN/GaN gates-separating groove heterostructure field-effect transistor (GSG HFET), in which a block barrier exists between the double gates as realized by dry etching. The current transport dominated by thermionic emission or thermionic field emission results in a high drain current density. The threshold voltage modulation mechanism of AlGaN/GaN GSG HFET is investigated. Due to the increasing of block barrier height and width, the threshold voltage shifts obviously towards to the positive direction with increasing the gate length or gate-to-gate distance ( L gg ). By optimizing the device structure, a threshold voltage of 1.8 V and a comparable drain current density of 550 mA/mm are obtained at L gg = 180 nm, while the values of 2.5 V and 370 mA/mm are obtained at L gg = 280 nm. Moreover, it's noteworthy that the threshold voltage is less sensitive to recess depth and etching time. The devices show high-uniformity threshold voltage within etching time range from 8 to 9 min.

Gallium oxide (Ga2O3) metal-oxide-semiconductor field-effect transistors (MOSFETs) were fabricated with gate recess depths of 110 nm and 220 nm, respectively. The gate recess was formed by dry plasma etching with Cr metal as the mask. The fabricated devices with a 25-nm HfO2 gate dielectric both showed a low off-state drain current of about 1.8 × 10−10 A/mm. The effects of recess depth on the electronic characteristics of Ga2O3 MOSFETs were investigated. Upon increasing the recess depth from 110 nm to 220 nm, the saturated drain current decreased from 20.7 mA/mm to 2.6 mA/mm, while the threshold voltage moved increased to +3 V. Moreover, the breakdown voltage increased from 122 V to 190 V. This is mainly because the inverted-trapezoidal gate played the role of a gate-field plate, which suppressed the peak electric field close to the gate.

Based on the excellent piezoelectricity of AlGaN/GaN heterostructures, a pressure sensor was fabricated combined with micro machining technology. Direct readout was realized by adopting Wheatstone bridge structure and the sensor showed favourable pressure responses. At the operation voltage of 5 V, the fabricated AlGaN/GaN pressure sensor exhibited a sensitivity of 7 μV/kPa with low non-linearity of 0.8% over a wide pressure range (from 0.1 to 5 MPa). As far as we know, this is a recorded responsive sensitivity in the reported direct-readout AlGaN/GaN pressure sensor.

An extensive investigation of fabricated AlGaN/GaN fin-shaped metal-insulator-semiconductor high-electron-mobility transistors (Fin-MISHEMTs) with Al2O3 dielectric is presented in this paper. Based on the pulsed I–V measurements and numerical simulation, the dynamic characteristics of GaN-based Fin-MISHEMTs were carried out under various quiescent bias conditions and temperatures. Moreover, the physical mechanisms of current collapse and dynamic on-resistance increase induced by trapping effects were analyzed. The results show that the observed nonmonotonic variation of current collapse with the gate quiescent bias voltage is resulted from the combination of gate leakage injection-related and hot-electron injection-related trapping effects. Compared with the conventional planar MISHEMTs, the current collapse of AlGaN/GaN Fin-MISHEMTs is smaller due to lower gate leakage and smaller threshold voltage shift, which is benefited from its enhanced gate controllability. The current collapse and dynamic on-resistance increase of Fin-MISHEMTs can be further suppressed by optimizing the device structure, such as designing the fin channels only under the gate.

Heteroepitaxial growth of conductive Si-doped β-Ga 2 O 3 films on c-plane sapphire substrates by metal-organic chemical vapor deposition (MOCVD) was successfully performed. The effect of Si content on the structural, morphological, electrical and optical properties of Si-doped β-Ga 2 O 3 films was investigated in detail. Distinctive surface morphology evolution of films depending on Si content was observed and presented. The Si-doped β-Ga 2 O 3 films exhibited high transmittance in the ultraviolet-visible regions. The temperature-dependent PL was carried out especially to discuss the photoluminescence properties of Si-doped β-Ga 2 O 3 films. More importantly, the results suggested that the conductivity of heteroepitaxial Si-doped β-Ga 2 O 3 films by MOCVD could be realized and controlled by adjusting the Si content. The minimum resistivity of 1.79×10 −1 Ω·cm was obtained for the films grown under the SiH 4 flow rate of 0.08 sccm.

We developed a new way to enhance the photoresponsivity of a van der Waals heterojunction p-n diode using surface acoustic waves (SAWs). The diode was constructed on top of a piezoelectric LiNbO3 substrate and composed of p-type black phosphorus (BP) and n-type molybdenum disulfide (MoS2) flakes that partly overlapped with each other. This layout facilitated the applied SAWs to rapidly drive carriers out of the depletion region. In this structural design, SAWs promoted the separation of photogenerated carriers, and thus greatly increased the photocurrent. The measured photocurrent for the device with SAWs was about 103 times higher than that of the device without SAWs. The device using SAWs showed a photoresponsivity as high as 2.17 A W-1 at the wavelength of 582 nm. This excellent performance was attributed to the SAWs suppressing electron-hole recombination in the device under light illumination. Our device exhibits promise as a high-performance photodetector and reveals new possibilities for acoustic devices in optoelectronics.

In this paper, we report on a novel E-mode AlGaN/GaN gates-seperating groove heterostructure field-effect transistor (GSG HFET). The current turn-on/off is controlled by changing gate voltage to regulate the horizontal energy band between the double gates. A threshold voltage of 0.23 V and a high drain current density of 851 mA/mm are obtained in GSG HFET. Compared with the proposed depletion-mode device, the maximum drain current of the GSG HFET deceases slightly (about 7%). It is noteworthy that the threshold voltage is less sensitive to the etching time. The devices show high-uniformity threshold voltage of 0.23 V within wide etching time range from 5 to 9 min.

Transition metal dichalcogenides (TMDCs) have recently become spotlighted as nanomaterials for future electronic and optoelectronic devices. In this work, we develop an effective approach to enhance the electronic and optoelectronic performances of WSe2-based devices by N2O plasma treatment. The hole mobility and sheet density increase by 2 and 5 orders of magnitude, reaching 110 cm2 V-1 s-1 and 2.2 × 1012 cm-2, respectively, after the treatment. At the same time, the contact resistance (Rc) between WSe2 and its metal electrode drop by 5 orders of magnitude from 1.0 GΩ μm to 28.4 kΩ μm. The WSe2 photoconductor exhibits superior performance with high responsivity (1.5 × 105 A W-1), short response time (2 ms), high detectivity (3.6 × 1013 Jones) and very large photoconductive gain (106). We have also built a lateral p-n junction on a single piece of WSe2 flake by selective plasma exposure. The junction reaches an exceedingly high rectifying ratio of 106, an excellent photoresponsivity of 2.49 A W-1 and a fast response of 8 ms. The enhanced optoelectronic performance is attributed to band-engineering through the N2O plasma treatment, which can potentially serve as an effective and versatile approach for device engineering and optimization in a wide range of electronic and optoelectronic devices based on 2D materials.

In this work, we presented a thin-film piezoelectric acoustic gas sensor with enhanced sensitivity by a surface modification strategy of oxygen plasma treated graphene oxide (GO) functionalization. By exposing to ammonia vapor (NH3) of various concentrations at controlled temperature and humidity, the characteristics of the GO-coated acoustic sensor were investigated, that is, sensitivity, linearity, response, and recovery time. Oxygen plasma treatment of the GO-coated sensor further enhanced the sensitivity compared with the freshly prepared GO-coated sensor. The mechanism of oxygen plasma treatment effect on the GO-coated sensor was discussed based on characterizations of X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscope (SEM), and precise weighing of the acoustic sensor. It was found that the oxygen plasma treatment introduces numerous defects to GO flakes, which are uniformly distributed across the GO surface, providing more gas molecule binding sites.

Graphene field-effect transistors (G-FETs) are being developed with ever increasing sensitivity as terahertz direct detectors at room temperature. The noise-equivalent power is being reduced towards the order of 1pW/Hz with frequency about 650 GHz. G-FET-based frequency multipliers and subharmonic mixers are becoming new active components for both millimeter and terahertz wave technologies. We report a 650-GHz G-FET coupled with terahertz antennas and a quasi-optical silicon lens for heterodyne/subharmonic detection. Heterodyne detection at 216 and 648 GHz, second-subharmonic detection at 432 GHz, and third-subharmonic detection at 648 GHz were demonstrated and characterized. Self-mixing/homodyne detection was used as a calibration tool for the power levels of the local pump source and the source to be detected. The conversion losses of heterodyne mixing at 216 GHz (off-resonant) and 648 GHz (resonant) were 38.4 dB and 57.9 dB with 12.8 dBm and −14 dBm of local pump power, respectively. The conversion loss of the second-harmonic mixing at 432 GHz is about 8 dB higher than that of the heterodyne mixing at 216 GHz. Calculations based on our quasi-static mixing model agree well with the measured conversion losses. To improve the conversion loss, more details on the G-FET noise, the optimal pump power, and the antenna should be examined.

Analog applications attract increasing interest for graphene field-effect transistors (GFETs). GFET with a cutoff frequency of up to 427 GHz has been reported; however, the device suffered from the large parasitic parameters and poor drain current saturation, which made their maximum oscillation frequency lower than the cutoff frequency. In this letter, quasi-free-standing bilayer graphene transistors with a gate length of 60 nm and ultra-thin gate dielectric are fabricated by an improved, self-aligned, process. Good gate coupling is achieved, and parasitic parameters are suppressed to a significant extent. The as-measured extrinsic cutoff frequency reaches 70 GHz and the maximum oscillation frequency reaches 120 GHz, which are the highest extrinsic frequencies reported for graphene transistors to date. Our results show the application potential of graphene RF devices in future high-speed electronic systems.

Understanding and engineering the interface between metal and two-dimensional materials are of great importance to the research and development of nanoelectronics. In many cases the interface of metal and 2D materials can dominate the transport behavior of the devices. In this study, we focus on the metal contacts of MoTe2 (molybdenum ditelluride) FETs (field effect transistors) and demonstrate how to use post-annealing treatment to modulate their transport behaviors in a controlled manner. We have also carried out low temperature and transmission electron microscopy studies to understand the mechanisms behind the prominent effect of the annealing process. Changes in transport properties are presumably due to anti-site defects formed at the metal–MoTe2 interface under elevated temperature. The study provides more insights into MoTe2 field effect devices and suggests guidelines for future optimizations.

We report a room-temperature, low-impedance and high-sensitivity terahertz direct detector based on bilayer graphene field-effect transistor (GFET). Epitaxially grown on silicon carbide, the bilayer graphene had an as-grown carrier mobility of 3000 cm 2 /Vs. The source/drain contacts were formed on the freshly cleaned graphene sheet to minimize the contact resistance and served also as terahertz antennas. The gate and the dielectric layer underneath with a length of 145 nm and a gap of 203 nm to the source/drain antennas were formed in a self-alignment process. Although the carrier mobility in the GFET was reduced to about 405 cm 2 /Vs, the high-quality ohmic contacts and the short graphene channel delivered an overall source-drain resistance less than 203 Ω. A voltage responsivity of 30 V/W and a noise-equivalent power of 51 pW/Hz 1/2 were estimated in direct detection at 0.33 THz. By using the GFET detector as a two-terminal detector, i.e., with the gate floating, a transmission-type terahertz imaging was demonstrated. Such a low-impedance GFET detector is ready to be matched to a commercial 50-Ω low-noise radio/microwave frequency amplifier allowing for high-speed homodyne detection and heterodyne detection in a quasi-optical configuration.

Three dimensional (3D) and two dimensional (2D) alternation growth was used to grow AlN epitaxial layers on sapphire substrates. AlN samples grown using this technique have higher crystalline quality and lower dislocation density than samples grown using only 3D or 2D growth modes as witnessed by the high-resolution X-ray diffraction. Smooth atomic terraces with root mean square roughness of 0.107 nm were observed using atomic force microscopy (AFM) when the 3D and 2D AlN were 75 nm and 425 nm, respectively. This sample possesses single crystallographic orientation along the c-axis identified by Raman spectroscopy. Furthermore, the 3D/2D alternating growth mode modulates internal stress in AlN epitaxial layer by adjusting 2D AlN thickness, and the mechanism was studied in detail.

The influence of mesa edge capacitance on the frequency characteristics of AlGaN/GaN HEMTs with 90 nm gate length was studied in this paper. To extract mesa edge capacitances, a small-signal equivalent circuit model considering mesa edge capacitances was provided. Based on the model, the intrinsic gate capacitances of AlGaN/GaN HEMTs with 2 × 20 μm, 2 × 30 μm, 2 × 40 μm, and 2 × 50 μm gate widths were extracted, respectively. Through linear fitting along gate width for the extracted results and simulations, 8.06 fF/μm2 of mesa edge capacitances at Vgs = −4.5 V and Vds = 8 V in the devices with 2 × 20 μm gate width was obtained, which can be about 33.2% of the total gate capacitance. Mesa edge capacitances results in a significant drop of current-gain cut-off frequency (fT), and the effect is more serious in the shorter gate length devices.

Using measured capacitance-voltage and current-voltage curves for the AlGaN/GaN heterostructure field-effect transistors with different source-drain spacing, the electron mobility under the gate region was obtained. By comparing mobility variation and analyzing polarization charge distribution, it is found that with device scaling, the effect of the diffused Ohmic contact metal atoms on the electron mobility is enhanced. Then, a theoretical calculation related to different scattering mechanisms was adopted and it was verified this enhanced effect is due to the enhanced polarization Coulomb field (PCF) scattering.

Nanomaterial based chemical sensors promise exceedingly high sensitivity with ultra-small form factors. However, fundamental limitations in selectivity and recovery speed have largely hindered their application in real-life scenarios. We report on a unique approach to improving the key performance of ZnO nanowire sensors by leveraging their resistive switching properties. By manipulating the resistive states of the nanowire, we were able to achieve excellent selectivity along with a significant improvement in recovery speed by more than 8 times. We attributed the enhancement to the switching between different electron transport mechanisms and redistribution of oxygen vacancies inside the one-dimensional channel. The innovative concept of incorporating sensing and resistive switching properties of nanostructures is particularly inspiring to the development of nanosensors to meet the versatile needs of real world applications.

The AlN/GaN heterostructure field-effect transistors with different GaN cap layer thicknesses were fabricated. With the calculated electron mobility and polarization charge distribution, the influence of different GaN cap layer thicknesses on electron mobility was determined by experiment and theoretical calculation. It is found that the increase of the GaN cap layer thickness can weaken the polarization Coulomb field scattering, and improve the electron mobility. This would be a possible approach to improve the performance of AlN/GaN HFETs by choosing a proper GaN cap layer thickness.

Ultra-thin InAlN/GaN heterostructure field-effect transistors (HFETs) having high maximum oscillation frequency (f max) are fabricated by scaling lateral dimensions. A 3 nm GaN cap layer is adopted to reduce the electron density and suppress the short-channel effects. Non-alloyed regrown n+-GaN ohmic contacts with total ohmic resistance (R tot) of 0.13 Ω.mm is also introduced into the device, in which the virtual source-to-drain distance is 600 nm. T-shaped gate with 40 nm length is formed in the centre of the source-to-drain region by self-aligned e-beam lithography. The peak extrinsic transconductance (g m) reaches 956 mS/mm. Most of all, a high f max of 405 GHz is obtained, which is the highest value among the reported InAlN/GaN HFETs. These obtained results mean that the InAlN/GaN HFETs having reliability should be still suitable for G-band (140–220 GHz) power-amplifier application with further optimisation.

We presented a GaN Schottky diode model with consideration of self-heating effect of devices in operation. The impact of diode chip temperature on the current and capacitance was taken into account in this model. The thermal resistance of diode chip was extracted by simulation combined measurement to calculate the temperature of Schottky junction with different pumping power. Advantages of established device model in the design of a 220GHz frequency doubler were presented in the end.

Mycobacterium tuberculosis (MTB) and non-tuberculous mycobacteria (NTM) are formidable causes of lung diseases throughout the world. While MTB is considered to be more virulent than NTM, host factors also play a key role in disease development. To elucidate whether there are differential immune responses to various mycobacteria, THP-1 macrophages were temporally infected with MTB H37Rv or with four different NTM species. We found that cells infected with MTB had greater bacterial burden and p65 nuclear factor-kappa B (NF-κB) activation than cells infected with NTM. There was also differential expression of mRNA for interleukin-1-β (IL-1β), IL-8, IL-10, and tumor necrosis factor-alpha (TNF-α) with no distinct pattern of mRNA expression among the different mycobacteria. In contrast, at the protein level, some generalizations can be made of the cytokines and chemokines expressed. Compared to uninfected cells, the rapid-growing Mycobacterium smegmatis but not Mycobacterium abscessus induced significantly greater pro-inflammatory cytokines and IL-10, whereas both NTM individually induced greater levels of chemokines. Compared to uninfected control cells, the two slow-growing NTM and MTB differentially induced cytokine expression with Mycobacterium avium inducing more pro-inflammatory cytokines and IL-10, whereas M. avium, Mycobacterium intracellulare, and MTB inducing greater but similar levels of chemokines. MTB-infected THP-1 cells also demonstrated lower level of phagosome–lysosome fusion and apoptosis than NTM-infected cells while there were differences in these macrophage functions among the NTM species. Interestingly, M. intracellulare, M. avium, and MTB have similar levels of autophagosome formation, but the levels displayed by all three were lower than for M. smegmatis and M. abscessus. This study demonstrates the differences in bacterial burden and macrophage effector functions among several clinically relevant mycobacterial species. Such disparities may, in part, account for differences in clinical outcomes among patients infected with various species of NTM as has been seen for different strains of MTB.

In this paper, we present a multifunctional metasurface enabling terahertz focusing for efficient terahertz wave control. Due to the sensitive response of two orthogonal electric dipoles to polarization direction of the terahertz wave, phase distributions on the metasurface can be efficiently controlled in both vertical and horizontal directions. Therefore, two different focal distances can be achieved under a normal incident wave with two different linear polarization. Further, the incident waves will form vertical or parallel axial focus with p(x) or s(y)-polarized component. In addition, this design method can be applied to other terahertz multifunctional devices which develops diversifications of the metasurface.

Nanosilver paste pressureless sintering for bonding power semiconductor devices have been widely used. However, most of the substrates used are silver- or gold-coated substrates. Additional coatings will increase the manufacture cost, reduce the production efficiency, and cause problems with the coating lamination. The bonding process was carried out by sintering nanosilver paste on bare copper DBC substrates in different reducing atmospheres in this study. Three different reducing atmospheres were used as comparison: i.e., (1) sintering in pure nitrogen (N2), (2) sintering in 4% hydrogen and 96% nitrogen (4%H2/N2), and (3) two-step sintering profile: drying in the air in the first step and then sintering in 4%H2/N2 in the second step. The bonding strength of sintered joints was evaluated by the shear test. The highest bonding strength can be obtained by the two-step sintering. The average shear strength obtained by the two-step sintering method is more than 40 MPa at the peak temperature of 310℃. It can be seen that the sintering atmosphere has a critical effect on the density of the joints. The sintered joints with the highest density were obtained by the two-step sintering method. Many necks were formed between the silver particles during the sintering.

Hydrogenated diamond MOSFETs with gate length of 350 nm are fabricated by a self-aligned process on (001)-oriented single crystal diamond substrate. The hydrogen-terminated diamond MOSFETs show maximum drain current density of 233 mA/mm at V GS =-4 V, and transconductance of 62 mS/mm. The maximum output power density reaches 815 mW/mm at 2 GHz, which is the highest reported value for diamond transistors measured at 2 GHz.

We have fabricated and characterized direct-coupled field-effect transistor (FET) logic (DCFL) Inverters based on monolithically integrated enhancement/depletion-mode (E/D-mode) InAlN/GaN high electron mobility transistors (HEMTs). The Enhancement-mode InAlN/GaN HEMT was realized by utilizing low damage BCl 3 -based plasma gate-recess etching, which exhibits a peak transconductance (G m ) of 435mS/mm with a threshold voltage of 0.74V. When the supply voltage (V DD ) is biased at 2.5V, the E/D InAlN/GaN HEMTs inverter exhibits an output logic swing of 2.19V, a logic-low noise margin of 0.54V and a logichigh noise margin of 1.38V.

4×4 H-SiC avalanche photodiode (APD) arrays with a high uniformity have been fabricated and characterized for ultraviolet (UV) detection in this work. A high optical gain of over 105 and a maximum unity-gain quantum efficiency of 68.2% at the wavelength of 282 nm are obtained for the 4HSiC APD pixels in the array. In addition, the APD arrays show high-uniformity breakdown voltage with a variation smaller than 1 V, and the dark currents of all the 16 pixels are below 1 nA at 95% breakdown voltage.

GaN Schottky diodes exhibit great potential for high power THz frequency multipliers. This paper presents thermal characterization results of GaN Schottky diodes in the frequency multipliers with flip-chip configuration. Common models of the different Schottky diode multiplier chip layouts are analyzed with 3-D thermal simulators. The thermal resistance results show that the GaN Schottky diodes chips have evident advantage in thermal management compared with GaAs chips. The differences of n -anode Schottky diodes chips in thermal effect are investigated in detail. The impacts of solders and filter substrate on thermal resistance are shown, which indicate the the filter substrate with high thermal conductivity will improve the performance of the THz frequency multipliers obviously.

&beta, Ga2O3 films were grown on sapphire (0001) substrates with various O/Ga (VI/III) ratios by metal organic chemical vapor deposition. The effects of VI/III ratio on growth rate, structural, morphological, and Raman properties of the films were systematically studied. By varying the VI/III ratio, the crystalline quality obviously changed. By decreasing the VI/III ratio from 66.9 &times, 103 to 11.2 &times, 103, the crystalline quality improved gradually, which was attributed to low nuclei density in the initial stage. However, crystalline quality degraded with further decrease of the VI/III ratio, which was attributed to excessive nucleation rate.

Layered black phosphorus (BP) has been expected to be a promising material for future electronic and optoelectronic applications since its discovery. However, the difficulty in mass fabricating layered air-stable BP severely obstructs its potential industry applications. Here, we report a new BP chemical modification method to implement all-solution-based mass production of layered air-stable BP. This method uses the combination of two electron-deficient reagents 2,2,6,6-tetramethylpiperidinyl- N-oxyl (TEMPO) and triphenylcarbenium tetrafluorobor ([Ph

Constructing a fingerprint database using the received signal strength is a widely used solution for indoor positioning to fit the positioning result online through matching the database with algorithm. Traditional fingerprint database construction methods are time-consuming and difficult to sample in special locations. In this paper, Kriging interpolation algorithm is proposed to interpolate or extrapolate fingerprint databases, in order to solve such problems, such as large workload, long time-consuming and difficult of sampling special features in the construction of fingerprint databases. The experiment is done using the Kriging algorithm and Inverse Distance Weighted algorithm to interpolate the database with 60% sampling points as known parameter. The experimental results show that the interpolation error of the Kriging algorithm is 4.49dBm, which is 5% lower than that by the Inverse Distance Weighted algorithm.

Figure S1. Characterization of BMSCs. Figure S2. The miRNA transfection efficiency and effect. Figure S3. miR-34a overexpression enhanced the osteoblastic differentiation of 4â Gy irradiated BMSCs in vitro. Figure S4. The siRNA transfection efficiency and effect. Figure S5. Distribution of agomiR in the bone defect area. Figure S6. Expression of miR-34a in the newly formed bone after implantation of miRNA delivery hydrogel. (DOCX 2001 kb)

Rationale: The association between non-tuberculous mycobacterial lung disease and alpha-1-antitrypsin (AAT) deficiency is likely due, in part, to underlying emphysema or bronchiectasis. But there is increasing evidence that AAT itself enhances host immunity against microbial pathogens and thus deficiency could compromise host protection. Objectives: The goal of this project is to determine if AAT could augment macrophage activity against non-tuberculous mycobacteria. Methods: We compared the ability of monocyte-derived macrophages cultured in autologous plasma that were obtained immediately before and soon after AAT infusion-given to individuals with AAT deficiency-to control an ex vivo Mycobacterium intracellulare infection. Measurements and Main Results: We found that compared to pre-AAT infused monocyte-derived macrophages plus plasma, macrophages, and contemporaneous plasma obtained after a session of AAT infusion were significantly better able to control M. intracellulare infection; the reduced bacterial burden was linked with greater phagosome-lysosome fusion and increased autophagosome formation/maturation, the latter due to AAT inhibition of both M. intracellulare-induced nuclear factor-kappa B activation and A20 expression. While there was a modest increase in apoptosis in the M. intracellulare-infected post-AAT infused macrophages and plasma, inhibiting caspase-3 in THP-1 cells, monocyte-derived macrophages, and alveolar macrophages unexpectedly reduced the M. intracellulare burden, indicating that apoptosis impairs macrophage control of M. intracellulare and that the host protective effects of AAT occurred despite inducing apoptosis. Conclusion: AAT augments macrophage control of M. intracellulare infection through enhancing phagosome-lysosome fusion and autophagy.

By the density functional theory (DFT) study, the adsorptions of the main surface precursors, MMAl and DMAlNH2, on the ideal and NH2-covered AlN(0001)-Al surfaces were investigated for AlN MOVPE process. By comparing the adsorption energies, the Mulliken Populations and the partial density of states (PDOS) for adsorbed atoms at different surface sites, it is found that on the ideal AlN surface, MMAl can be stably adsorbed at T4, H3 or Br sites with similar probabilities; DMAlNH2 can be stably adsorbed at Top-Top or 3Top sites, with dissociative adsorption occurring at the latter site. On the NH2-covered surface, MMAl can be stably adsorbed at T4 and H3 sites with similar probabilities; while DMAlNH2 can be stably adsorbed at only Top site. On the Al-terminated ideal AlN surface, the adsorption of DMAlNH2 is more stable than that of MMAl; while on the N-terminated (NH2-covered) AlN surface, the adsorption of MMAl is much more stable than that of DMAlNH2.

AlGaN/GaN high-electron-mobility transistors (HEMTs) with postpassivation plasma treatment are demonstrated and investigated for the first time. The results show that postpassivation plasma treatment can reduce the gate leakage and enhance the drain current. Comparing with the conventional devices, the gate leakage of AlGaN/GaN HEMTs with postpassivation plasma decreases greatly while the drain current increases. Capacitance–voltage measurement and frequency-dependent conductance method are used to study the surface and interface traps. The mechanism analysis indicates that the surface traps in the access region can be reduced by postpassivation plasma treatment and thus suppress the effect of virtual gate, which can explain the improvement of DC characteristics of devices. Moreover, the density and time constant of interface traps under the gate are extracted and analyzed.

The impact of strain on optical polarization of c-plane Al0.37Ga0.63N/Al0.5Ga0.5N multiple quantum wells (QWs) has been studied by the polarized photoluminescence spectroscopy at room temperature. By adopting multiple alternation cycles of low- and high-temperature growth, the strain state of AlN template can be modulated. With increasing in-plane compressive strain of QWs layers, the polarization degree can be enhanced from 41.5% to 61.9%. Furthermore, the strain dependence of the polarization degree has been confirmed by the numerical simulation based on k·p method, revealing the dominant role of energy level shift and wavefunction overlap. It is found that the relative position of the three valence subbands is responsible for the steep increase of the polarization at smaller strain, while the wavefunction overlap induced by piezoelectric effect modulates the optical polarization at larger strain. These results are of great importance in the design and analysis of AlGaN based ultraviolet light emitting devices.

Numerical study on the influence of inlet structure of planetary reactor on gas reaction path and growth rate in AlN-MOVPE was investigated. It was found that, for the conventional two-inlet reactor (base reactor), the reaction is dominated by the adduct reaction path, and the growth rate is low but evenly distributed; for the inverted inlet reactor, i.e., group-III in lower inlet and group-V in upper inlet, the reaction is dominated by the pyrolysis path, and the growth rate is higher than the base reactor but the growth uniformity is decreased. By moving the position of the inlet separator closer to the ceiling for the inverted inlet, the growth uniformity is improved. When the number of reactor inlets increases from two inlets (base reactor) to three and five inlets, the growth rate increases, the growth uniformity improves, and the reaction changes from the adduct-dominated path to the pyrolysis and adduct coexisted path. Besides varying the inlet geometry, we also found that decreasing the NH3 flow rate will enhance the pyrolysis path and the growth rate for the above reactors.