High performance oscillator with 2-mW output power at 300 GHz

Material structures and device structures of a 100-GHz InP based transferred-electron device are designed in this paper. In order to successfully fabricate the Gunn devices operating at 100 GHz, the InP substrate was entirely removed by mechanical thinning and wet etching. The Gunn device was connected to a tripler link and a high RF(radio frequency)output with power of 2 mW working at 300 GHz was obtained, which is high enough for applications in current military electronic systems.     

Dispersion effect on the current voltage characteristic of AlGaN/GaN high electron mobility transistors

The current voltage (IV) characteristics are greatly influenced by the dispersion effects in AlGaN/GaN high electron mobility transistors. The direct current (DC) IV and pulsed IV measurements are performed to give a deep investigation into the dispersion effects, which are mainly related to the trap and self-heating mechanisms. The results show that traps play an important role in the kink effects, and high stress can introduce more traps and defects in the device. With the help of the pulsed IV measurements, the trapping effects and self-heating effects can be separated. The impact of time constants on the dispersion effects is also discussed. In order to achieve an accurate static DC IV measurement, the steady state of the bias points must be considered carefully to avoid the dispersion effects.     

Kink effect in current–voltage characteristics of a GaN-based high electron mobility transistor with an AlGaN back barrier

The kink effect in current–voltage(IV)characteristic s seriously deteriorates the performance of a GaN-based HEMT.Based on a series of direct current(DC)IV measurements in a GaN-based HEMT with an AlGaN back barrier,a possible mechanism with electron-trapping and detrapping processes is proposed.Kink-related deep levels are activated by a high drain source voltage(Vds)and located in a GaN channel layer.Both electron trapping and detrapping processes are accomplished with the help of hot electrons from the channel by impact ionization.Moreover,the mechanism is verified by two other DC IV measurements and a model with an expression of the kink current.     

兰州冷却储存环上可开展的强子物理研究

介绍了当前强子物理的研究现状和兰州冷却储存环的能量特点，以及国内强子物理专家的分析和建议。在兰州冷却储存环上，可利用中能轻离子束核反应产生强子激发态研究强子内部夸克态的结构和性质、强子性质随核环境的变化和手征对称破缺与部分恢复。尤其是通过兰州冷却储存环上限能区附近的P＋P反应，研究奇异夸克的不对称性和形状因子，寻找超子激发态和pentaquark的实验证据，发现双重子态的实验事例。 According to both the development on badrons physics and the aspect of Lanzhou cooling storage ring （CSR） and based on the analysis and propositions given by experts in China, we propose some hadrons physics program at CSR. The hadron spectroscopy produced in light nucleus collisions at CSR used to probe the quark and gluon structure of hadrons, to study the modification of the hadron properties in nuclear matter and to investigate the spontaneous breaking of the chiral symmetry and its partial restoration. Especially, the proton-proton collisions at beam energies per proton below 2.8 GeV at CSR should be used to measure the strangeness asymmetry and strange form lector, to probe the existence of hyperon and pentaquarks and to find the evidence for the existence of dibaryon.     

熔融碳酸盐燃料电池阳极材料表面改性

选择铌作为合金化元素，通过氟化物熔盐电化学表面合金化的方法对熔融碳酸盐燃料电池阳极材料镍进行表面改性，改性后的阳极材料的耐蚀性能与电催化性能均得到明显的改善。     

Influences of high-temperature annealing on atomic layer deposited Al2 O3/4H-SiC

High-temperature annealing of the atomic layer deposition (ALD) of Al2O3 films on 4H-SiC in O 2 atmosphere is studied with temperature ranging from 800℃ to 1000℃. It is observed that the surface morphology of Al2O3 films annealed at 800℃ and 900℃ is pretty good, while the surface of the sample annealed at 1000℃ becomes bumpy. Grazing incidence X-ray diffraction (GIXRD) measurements demonstrate that the as-grown films are amorphous and begin to crystallize at 900℃. Furthermore, C-V measurements exhibit improved interface characterization after annealing, especially for samples annealed at 900℃ and 1000℃. It is indicated that high-temperature annealing in O2 atmosphere can improve the interface of Al2O3 /SiC and annealing at 900℃ would be an optimum condition for surface morphology, dielectric quality, and interface states.     

Improvement of breakdown characteristics of an A1GaN/GaN HEMT with a U-type gate foot for millimeter-wave power application

<正>In this study,the physics-based device simulation tool Silvaco ATLAS is used to characterize the electrical properties of an AlGaN/GaN high electron mobility transistor(HEMT) with a U-type gate foot.The U-gate AlGaN/GaN HEMT mainly features a gradually changed sidewall angle,which effectively mitigates the electric field in the channel, thus obtaining enhanced off-state breakdown characteristics.At the same time,only a small additional gate capacitance and decreased gate resistance ensure excellent RF characteristics for the U-gate device.U-gate AlGaN/GaN HEMTs are feasible through adjusting the etching conditions of an inductively coupled plasma system,without introducing any extra process steps.The simulation results are confirmed by experimental measurements.These features indicate that U-gate AlGaN/GaN HEMTs might be promising candidates for use in miltimeter-wave power applications.     

High-mobility SiC MOSFET with low density of interface traps using high pressure microwave plasma oxidation

The microwave plasma oxidation under the relatively high pressure(6 kPa)region is introduced into the fabrication process of SiO2/4 H-SiC stack.By controlling the oxidation pressure,species,and temperature,the record low density of interface traps(~4×10¹⁰cm^-2·eV^-1@Ec-0.2 eV)is demonstrated on SiO2/SiC stack formed by microwave plasma oxidation.And high quality SiO2 with very flat interface(0.27-nm root-mean-square roughness)is obtained.High performance Si C metal–oxide–semiconductor field-effect transistors(MOSFETs)with peak field effect mobility of 44 cm^-2·eV^-1is realized without additional treatment.These results show the potential of a high-pressure plasma oxidation step for improving the channel mobility in SiC MOSFETs.     

The design and manufacture of a notch structure for a planar InP Gunn diode

A planar InP-based Gunn diode with a notch doping structure is designed and fabricated for integration into millimeter-wave and terahertz integrated circuits.We design two kinds of InP-based Gunn diodes.One has a fixed diameter of cathode area,but has variable spacing between anode and cathode;the other has fixed spacing,but a varying diameter.The threshold voltage and saturated current exhibit their strong dependences on the spacing(10 μm-20 μm) and diameter(40 μm-60 μm) of the InP Gunn diode.The threshold voltage is approximately 4.5 V and the saturated current is in a range of 293 mA-397 mA.In this work,the diameter of the diode and the space between anode and cathode are optimized.The devices are fabricated using a wet etching technique and show excellent performances.The results strongly suggest that low-cost and reliable InP planar Gunn diodes can be used as single chip terahertz sources.