Abstract:The simulation of the semiconductor 3D device is performed to establish the 3D damagemodel to study the damage mechanism of the Single Event Effects(SEE) in SiGe Heterojunction Bipolar Transistor(HBT), as well as the key factors influencing the Single Event Effect under the coupling action of different working modes and extreme space environment. The transient current changes of each terminal are analyzed and compared after the ions striking on the device under different conditions. The results show that under different operating voltages, the degree of SEE damage is different in different extreme temperatures and different ion radiation environments, which is related to the ionization of carriers in different environments within the device.

Abstract:Four types of NOR Flash memories from different manufacturers with 90 nm feature sizes are studied, based on the HI-13 accelerator of the China Academy of Atomic Energy. Aiming to evaluate the Single Event Upset(SEU) effect for those memories, heavy-ion with different Linear Energy Transfer(LET) values is utilized to irradiate the devices. Both static and dynamic tests are performed to obtain the SEU cross-section of the device. Test results show that the memory with large capacities has a slightly bigger SEU cross-section than the devices with small capacities. There is almost no impact on the SEU cross-section of the device with or without bias. The SEU cross-section of the domestic alternative devices is bigger than that of two foreign commercial devices. The LET threshold of the domestic alternative devices is nearly at 12.9 MeV·cm²/mg, while that value of foreign commercial devices between 12.9~32.5 MeV·cm²/mg. The SEU cross-section results from static and dynamic tests have good consistency, which indicates test mode has no obvious influence on SEU effect. In addition, the synergistic effects of Single Event Effect(SEE) and Total Ionizing Dose(TID) effect for Flash memory are also studied, the results show that TID dose will increase the sensitivity of the device to SEE. The analysis shows that the ionization caused by the TID effect leads to the electron leakage from the floating gate and the drift of transistor threshold voltage, therefore SEU is more likely to occur on the basis of TID effect.

Abstract:Based on the sixth-generation 650 V SiC Junction Barrier Schottky(SiC JBS) diode and the third-generation 900 V Silicon Carbide Metal-Oxide Semiconductor Field-Effect-Transistor(SiC MOSFET), the single event effect, total dose effect and displacement damage effect of SiC power devices are studied. In the 20~80 MeV proton single event effect experiment, the Single Event Burnout (SEB) of SiC power device is accompanied by the generation of wave-shaped pulse current, and the breakdown characteristics of SEB devices are completely lost after irradiation. The accumulated proton fluence that induces SEB in SiC power devices decreases with the increase of bias voltage. In the single event effect simulation of SiC MOSFET, when heavy ions are incident on the device from the source, there exit a shorter SEB occurrence time and a lower SEB threshold voltage. The gate-source corner and the substrate-epitaxial layer junction are SEB sensitive regions of SiC MOSFET. The coexistence of strong electric field strength and high current density leads to excessive lattice temperature in the sensitive regions. When studying Co⁶⁰ source total dose effect for SiC MOSFETs at gate bias (U_GS=3 V, U_DS=0 V), more serious electrical characteristics degradation occurs compared to at drain bias(U_GS=0 V, U_DS=300 V) and zero voltage bias (U_GS=U_DS=0 V). Using the middle-band voltage method, it is found that the vertical electric field in the oxide layer under gate bias increases the generation rate of trapped charges and exacerbates the degradation of threshold voltage. The neutron displacement damage leads to the reduction of forward and reverse currents in SiC JBS diodes. The neutron displacement damage effect experiments are carried out under the drain bias, and the electrical characteristics of SiC MOSFET are degraded the most significantly. This work provides a certain reference and support for the research on the radiation effect mechanism and radiation hardening of SiC devices for space application.

Abstract:In order to study the effect of H₂ and H₂O on the radiation effect of domestic bipolar devices, a typical gate-controlled bipolar transistor is designed, and the irradiation tests in different concentrations of H₂ are carried out, as well as the total dose irradiation tests after the temperature and humidity tests. The results show that the anti-radiation ability of the device decreases gradually with the increase of hydrogen concentration. After the temperature and humidity test, the radiation damage of the device increases with the entry of H₂O. On this basis, gate scanning method is employed to quantitatively separate the radiation-induced defects of the oxide layer. It is found that both H₂ and H₂O will cause the increase of the radiation-induced interface trap charge Nit after entering into the oxide layer. In addition, the potential mechanism of H₂ and H₂O induced damage enhancement is given by theoretical analysis. The research results are of great value to the evaluation of the anti-radiation performance of electronic systems in radiation environment.

Abstract:The effect of total ionizing dose on the time-dependent breakdown characteristics of the high dielectric constant HfO₂-based gate dielectric used in nano-Metal-Oxide-Semiconductor(MOS) devices has been investigated. The MOS capacitor with HfO₂-based gate dielectrics is taken as the research object, a total dose ionization irradiation experiment of ⁶⁰Co-γ rays with different gate biases is carried out. The test results of current-voltage, capacitance-voltage and time-dependent dielectric breakdown characteristics of MOS capacitor before and after irradiation are compared. The results show that the damage characteristics of MOS capacitors are different under different irradiation bias conditions. Under positive bias irradiation, the gate current increases significantly at low gate voltage, and the slope of capacitance-voltage characteristic decreases. Under zero bias irradiation, the gate current and capacitance increase significantly at high forward gate voltage. Under negative bias irradiation, the gate current increases, the capacitance increases under high forward gate voltage while the capacitance slope decreases. The time-dependent breakdown voltage of the capacitor decreases significantly under all three bias conditions. This study provides a reference for the long-term reliability study of nano-MOS devices in radiation environments.

Abstract:The total ionizing dose effect of Silicon Carbide(SiC) Metal-Oxidel-Semiconductor Field Effect Transistor(MOSFET) at different temperatures is studied. Three SiC MOSFET devices manufactured at home and abroad are irradiated by ⁶⁰Coγ ray. The radiation damage characteristics of threshold voltage, breakdown voltage, conduction resistance and leakage current are obtained at 25 ℃, 100 ℃ and 175 ℃, respectively. The degradation degree of the devices after irradiation at different temperatures are compared. The results show that the threshold voltage, static leakage current and sub-threshold characteristics of different devices are sensitive to ambient temperature, while the on-resistance and breakdown voltage are relatively insensitive. In addition, the sensitivity of the total ionizing response of SiC MOSFET to ambient temperature also varies with different manufacturers. It is found that the threshold voltage, static leakage and other parameters decrease with the increase of temperature due to the the tunneling annealing effect during high temperature irradiation.

Abstract:Charge-Coupled Devices(CCD) is an image sensor used for visible light imaging in space photoelectric systems. For the ground simulation test of the space radiation effect of CCD, it is necessary to use appropriate bias conditions to analyze the space radiation damage of CCD. Because CCD is very sensitive to the total ionizing dose effect and displacement effect, it is of great significance to study the radiation effect and damage mechanism of CCD under different bias conditions because of the threat of the damaging effect faced by CCD space application. In this paper, γ-ray, and proton irradiation experiments are carried out on a buried channel CCD device under different bias conditions. The degradation rules of the total ionizing dose and displacement damage about radiation-sensitive parameters such as dark current and spectral response of CCD are obtained; as well as the damage mechanism of irradiation bias on the radiation effect of CCD. The results show that the bias of CCD under γ-ray irradiation has an important effect, but there is no obvious effect under proton irradiation. Meanwhile, the radiation damage mechanism of CCD is analyzed according to the structure of CCD and the results of the annealing test after irradiation.

Abstract:GaN High-Electron-Mobility Transistors(HEMTs) devices bear the characteristics of high frequency resistance, high temperature resistance, high power and radiation resistance, which have broad application prospects in radiation environments such as nuclear reactors, cosmic detection and other radiation environments. Therefore, Stopping and Range of Ions in Matter(SRIM) is employed to simulate the effect of 1.8 MeV proton radiation on the conventional depletion device with different AlGaN barriers, and to observe the change law of vacancy density with depth. Under the optimal AlGaN barrier thickness, the MIS-HEMT devices of five different gate oxygen layer materials are simulated and compared. It is found that the material of Aluminum Nitride(AlN) gate oxygen layer bears relatively good radiation resistance.

Abstract:Terahertz communication has become one of the key candidate techniques for future 6G mobile communication to realize "communication with full spectra" because of its rich spectrum resources. Due to the unique advantages such as simple structure, easy integration, low cost and low power consumption, the incoherent photonics-assisted terahertz communication system based on envelope detection technique has been widely concerned and favored by the researchers. By summarizing the structure, characteristics and key techniques of incoherent photonics-assisted terahertz communication systems, current research status and outstanding achievements of the terahertz envelope detectors and the incoherent photonics-assisted terahertz communication systems at home and abroad in recent years are introduced. In addition, the incoherent photonics-assisted terahertz communication system based on amplitude modulation and In-phase Quadrature(IQ) modulation are discussed in detail, and the advantages and disadvantages of each system are also compared. Finally, the future development directions of 6G-oriented incoherent photonics-assisted terahertz communication systems and the crucial devices are expected.

Abstract:Graphene is attractive for the great potential in microwave, millimeter wave, terahertz wave and other fields due to their excellent electronical properties. In this paper, a rectangular metallic waveguide integrated with graphene for phase and amplitude modulator is designed in the millimeter and sub-terahertz waves frequencies. Through adjusting the surface impedance of graphene, the amplitude and phase of electromagnetic wave propagation in the waveguide can be controlled dynamically. Meanwhile, the influence of the length and position of the integrated graphene sheet on the transmission and reflection coefficients of electromagnetic wave in the waveguide is analyzed, as well as the effect of graphene chemical potential on the transmission and reflection of electromagnetic wave in waveguide. The results show that the reflection coefficient, transmission coefficient and transmission phase modulation range of the modulator can be customized by adjusting the length of graphene sheet and its position in rectangular metal waveguide, which meets the needs of device level applications.

Abstract:Terahertz radar bears the advantages of high resolution and high frame rate. It is one of the current research hotspots in the field of terahertz. Aiming at the demand for real-time ground imaging and moving target tracking, a Ground Moving Target Indication(GMTI) processing algorithm based on wide band Space-Time Adaptive Processing(STAP) is proposed. The radar imaging and Multi-channel GMTI are achieved simultaneously on the airborne terahertz radar for the first time. The effectiveness of the algorithm is verified by the experimental data of the airborne terahertz radar.

Abstract:Under large-angle conditions, the problem of amplification or even mutation of attitude error would arise in the attitude measurement methods based on accelerometers or gyroscopes. For the large pitch angle measurement, the arrangement of redundant accelerometers can be determined by preset Euler rotation method, which reduces the pitch angle measurement error. For the roll angle measurement under the condition of large pitch angle, a decoupling attitude determination algorithm based on angular rate threshold is proposed. When the actual pitch rate is greater than the threshold value, the angular velocity projection method can suppress the drift of the roll angle error. When the actual pitch rate is less than the threshold value, the angular velocity integration method can avoid the enlargement of the attitude error caused by angular velocity projection. Through theoretical derivation, analysis and simulation, the preset Euler rotation method can effectively avoid the amplification of the pitch angle attitude error under the condition of large pitch angle, and the gyro decoupling attitude measurement algorithm can maintain the roll angle accuracy for a long time in an oscillating environment.

Abstract:Multifunctional Integrated RF System(MIRFS) is an important way to integrate various RF functions of shipborne, airborne, spaceborne and other space-limited platforms, such as radar, wireless communication, electronic warfare, navigation and positioning, and its core is aperture integration, RF integration and software integration. Aiming at the multi-task sharing requirement of RF integration for MIRFS, a multichannel all-digital transmitter architecture is proposed. This architecture has the data channels with independent parameters configuration, each channel starts by digitally orthogonal up-conversion of the input baseband I/Q data to an appropriate Intermediate Frequency(IF). Then, two pairs of inverting digital pulse sequences are generated by pulse coding of IF I/Q data with two pairs of Band-Pass Delta Sigma Modulator(BPDSM). The BPDSM pulse sequences generated by all channels are interpolated, and the data are finally integrated into 1-way digital pulse sequences through data interweaving, so as to realize the digital synthesis of multi-channel RF modulation signals. Simulation shows that the architecture can improve the flexibility and adaptability of MIRFS by independently configuring multiple channel parameters.

Abstract:Based on the working principle of Artificial Magnetic Conductor(AMC), a low Radar Cross Section(RCS) microstrip antenna with operating frequency in X-band is designed. Firstly, an AMC cell is designed, and the reflected phase difference of 180°±37° is obtained by the vertical incidence of X and Y polarized waves in the 8.6~14.6 GHz band range. Then, the AMC chessboard structure reflector is composed of 3×3 elements. The simulation results show that the reflector has smaller backward RCS than the Perfect Electric Conductor(PEC) plate with the same size. Finally, the AMC structure is arranged in coplanar with the microstrip antenna at 10 GHz, which maintains the good radiation performance and profile height of the original antenna, and achieves the RCS reduction of not less than 7.5 dB for the vertical incidence of two polarized waves in the frequency range of 8.4~14.8 GHz.

Abstract:An efficient spectral clustering algorithm based on subspace decomposition is proposed. Firstly, based on the matrix decomposition of consensus information and domain specific information, the linked documents are divided into three subspaces, the different effects of consensus information and domain specific information on clustering are modeled by adding regularization items to the subspaces, and the alternative optimization method is utilized to achieve spectral clustering. In addition, considering the complexity of spectral clustering, a gradient descent method with curvilinear search is proposed to accelerate the solution process. Experimental results on three real datasets show that the proposed algorithm is superior to the current typical baseline algorithm in terms of clustering quality and efficiency, and is insensitive to input parameters.

Abstract:The working principle of pulse-dilation framing camera and Rayleigh criterion are introduced. The spatial resolution and modulation on-axis of pulse-dilation framing camera are calculated by using Rayleigh criterion through building model, simulating magnetic field, tracking electron trajectory and fitting histogram of imaging distribution. The research results show that, when the 10 000 electrons are emitted from adjacent object points on the photocathode, the imaging modulation of two fully distinguishable adjacent object points is 98.5732%, the spatial resolution is 194.523 7 μm; the modulation of just distinguishable is 19.16%, the spatial resolution is 73.22 μm; the modulation of undistinguishable is 0.14%, the spatial resolution is 4.7 μm. This work can provide a visualized solution for calculating spatial modulation transfer function of 2D ultrafast diagnosis device.

Abstract:Steady-state X-ray source is an important radiation simulation device, which has important applications in research fields such as radiation effects. Electron emission occurs when X-ray bombards the target. Long-term bombarding will cause the accumulation of charge on the surface of the material or the effect of electron multiplication, which will lead to the change of material properties. The Monte Carlo simulation method is applied to calculate the X-ray energy spectrum at tube voltages of 50 kV, 150 kV and 225 kV, and the electron emission under X-ray irradiation is simulated. The focal spot distribution of X-ray and the dispersion of electron emission with collimating hole diameters of 2 mm, 4 mm and 6 mm are studied respectively, and the characteristics of electron emission energy spectrum and current intensity generated by X-ray bombardment of different energy spectra on samples such as polyethylene, polyimide, Si, SiO₂, Cu, Ta and W are also studied, which can provide theoretical basis and guidance for the experimental research and design of electron emission characteristics of materials under X-ray irradiation.