Rongxing Cao

In this paper, the influence mechanism of total ionizing dose (TID) effect on the single-event burnout (SEB) sensitivity of enhancement-mode AlGaN/GaN HEMTs was investigated by a combined method of experiment and simulation. Gamma-ray irradiation significantly affects the electrical characteristics of the device, with a 0.16V decrease in threshold voltage and a substantial increase in leakage current at a dose of 900 krad(Si). Further single-event effect experiments showed that for the devices pre-irradiated with TID, the threshold voltage of SEB was reduced by 100 V. Utilizing TCAD simulation, it was found that gamma-ray irradiation induces a large number of fixed positive charges and defect states in regions such as the device barrier layer and heterojunction interface, leading to the increase of internal electric field intensity, impact ionization rate, and local lattice temperature. These factors jointly reduce the voltage threshold of SEB and ultimately enhance the SEB susceptibility of the device.

Purpose: SiC MOSFETs are widely used in aerospace and power electronics owing to their superior electrical properties, yet they suffer from combined threats of space radiation and thermo-electrical stress fatigue. This study aims to explore the influence of electron irradiation on the power cycling lifetime of SiC MOSFETs and reveal the corresponding failure mechanisms, offering a theoretical basis for the reliability evaluation of SiC MOSFETs in space radiation environments. Design/methodology/approach: Experiments were conducted using 10 MeV electron irradiation at doses of 3 Mrad, 5 Mrad and 10 Mrad(Si), followed by forward-mode power cycling tests. Electrical parameters including threshold voltage and on-resistance were monitored periodically. Optical microscopy was adopted to characterize bond wire and solder layer damage. Electro-thermal-mechanical coupling simulation and Geant4 simulation were applied to analyze the internal stress distribution and energy deposition, clarifying the failure evolution process. Findings: Electron irradiation induces negative drift of threshold voltage and reduction of on-resistance via gate oxide charge trapping. During power cycling, threshold voltage shifts positively and on-resistance rises significantly with cycling count, and higher irradiation dose aggravates the drift amplitude. Electron irradiation drastically shortens the power cycling lifetime, which is reduced by 60% at 10 Mrad compared with unirradiated devices. Irradiation creates lattice defects in the solder layer, forming voids under cyclic thermal stress, which intensifies stress concentration at bond wire-chip joints and accelerates bond wire lift-off as the final failure mode. Originality/value: This study systematically reveals the synergistic degradation mechanism of electron irradiation and power cycling on SiC MOSFETs, distinguishing chip-level electrical parameter degradation and package-level mechanical failure. It provides key data and mechanistic support for the lifetime prediction and reliability optimization of SiC power devices in space applications.

NAND Flash memory, featuring high-speed read/write capability, high-density storage, and low power consumption, is widely employed in satellite, detector, and spacecraft storage systems. With the increasing proliferation of electronic devices, there has been a corresponding rise in research and attention towards the single event effect (SEE) induced by high-energy electrons in flash memory technologies. In this work, a simulation study is conducted to investigate data bit upsets in NAND Flash memory induced by high-energy electrons. The results show that high-energy electrons can trigger both SEE and total ionizing dose effect (TID) in the floating-gate cells, resulting in threshold voltage shifts and data bit reversals. At lower electron energies, the synergistic interaction becomes more pronounced with increasing energy, leading to an increase in the upset cross-section. When the electron energy reaches 10 MeV, the upset cross-section attains its maximum and then tends to stabilize. This behaviour is mainly attributed to the maximum energy deposition in the sensitive region of the floating-gate cell, where the TID-induced degradation significantly enhances its SEE sensitivity.

The impact of total ionizing dose (TID) on radio frequency (RF) fingerprints of Long Range (LoRa) devices was investigated through ⁶⁰Co-γ irradiation. RF signals were collected under different accumulated doses, t-SNE (t-distributed stochastic neighbor embedding) visualization indicates that inter-class separability of the extracted features decreases with increasing dose, closely correlating with the decline in fingerprint recognition accuracy. And at accumulated doses above 200 krad(Si), communication failures were observed in some devices. Although residual features remained detectable, recognition accuracy dropped substantially, demonstrating that radiation exerts a pronounced adverse effect on RF fingerprint identification. Furthermore, the carrier frequency offset (CFO) together with nonlinear characteristics of the power amplifier (PA) that related to the source of the RF fingerprint of LoRa devices are analyzed. The results show that TID induces performance degradation in both the temperature-compensated crystal oscillator (TCXO) and the PA. The TCXO exhibits carrier frequency drift, while the PA shows amplitude–phase (AM–PM) distortion, both of which significantly reduce the stability and consistency of RF fingerprints.

The rise of the 2D ferromagnets not only significantly advances fundamental physics and materials science but also provides excellent opportunities for various applications, particularly in spintronics. The 2D ferromagnets reported so far either show a Curie temperature ( T _c ) below room temperature (RT) or possess a high magnetic damping ( α ), which strongly limits their applications. Here, utilizing a state‐of‐the‐art interconnected molecular beam epitaxy and magnetron sputtering system, we fabricate high‐quality self‐intercalated Cr _1.8 Te ₂ films and Cr _1.8 Te ₂ /Pt heterostructures with clean interfaces. We find that the Cr _1.8 Te ₂ simultaneously achieves a high T _c (∼340 K) and a record‐low α (∼0.02) among all 2D ferromagnets with T _c exceeding RT. These unique features enable the first observation of spin injection from a 2D ferromagnet via spin pumping in Cr _1.8 Te ₂ /Pt bilayers under ambient conditions. Our findings establish self‐intercalated Cr _1.8 Te ₂ as an efficient spin current source at RT, highlighting its great potential for practical spintronic applications.

Nickel-doped bismuth selenide (Bi₂Se₃) polycrystalline material, synthesized via a solvothermal method, emerged as a dual-functional material for mid-temperature optoelectronic and thermoelectric applications. Structural analysis revealed a rhombohedral phase with a new (0 1 8) peak and a 39% reduced crystallite size alongside morphological transitions to spherical and rod-like grains. Nickel doping narrowed the optical bandgap by 50%, enabling broadband absorption (317–678 nm) and inducing a 500 nm photoluminescence redshift for near-infrared emission. Thermoelectrically, nickel doping enhanced the electrical conductivity by 220% at 425 K while maintaining a high Seebeck coefficient and reducing the lattice thermal conductivity by 19%. These coordinated improvements yielded a record thermoelectric figure of merit (ZT = 1.15 at 525 K) for Ni₀.₃Bi₂Se₃a 259% enhancement over undoped Bi₂Se₃. The work establishes nickel-doped Bi₂Se₃ as a scalable and cost-effective material for high-efficiency photonic devices and waste-heat recovery systems, addressing critical challenges in sustainable energy technologies in the mid-temperature range.

This study investigates the effect of temperature on leakage current degradation in p-GaN gate high electron mobility transistors (HEMTs) under heavy ion irradiation. Experimental results show that Kr ion irradiation at room temperature significantly increases drain leakage current, primarily along the source-drain path. The device undergoes electrical degradation, with a 5.2% positive shift of V _TH and a 26.5% reduction of output current. At higher temperatures (350 K–400 K), the distribution of leakage path remains in different regions of gate-to-drain. Hole accumulation beneath the gate increases the electric field in the p-GaN layer, raising the risk of single-event gate rupture and single-event burnout. Utilizing TCAD simulation, the temperature effect on the leakage path distribution can be attributed to the temperature-related electric field, lattice temperature, and carrier thermal excitation and tunneling. These findings provide theoretical insights for understanding the single-event leakage current characteristics of p-GaN gate HEMTs in space radiation environments.