Search

In this paper, the total ionize dose (TID) irradiations for NPN bipolar transistors were carried out by 60Co γ rays. Obvious degradations were observed after irradiation, which are manifested as the increase of base current and the decrease of current gain. A more obvious increase of base current was observed at lower emitter junction bias. It shows that the degradation of the base current mainly origins from the increase of the recombination current of the emitter junction, since the recombination current component in base current is dominant at lower emitter junction bias. It can be concluded that the performance degradations of bipolar transistors are mainly due to the increase of recombination current caused by radiationinduced traps in the oxide. It is found that the bias condition during irradiation is the key factor affecting the TID effect of NPN transistor. The reverse bias is a worse bias condition than the zero bias during irradiation. Furthermore, the TID effect of two kinds of NPN bipolar transistors was compared. The two kinds of transistors have the same structure, except that one of the devices is radiation hardened by improving the surface state of the base region. The radiation induced degradations in radiation hardened devices are less than that in unhardened devices. For the unhardened device, the base current increases from 882×10-8 A to 367×10-7 A at |VEB|=05 V after 50 krad(Si) irradiation, increased by 316%. While for the hardened device, the base current increases from 751×10-8 A to 119×10-7 A at |VEB|=05 V after 50 krad(Si) irradiation, increased by 584%. Finally, the deep level traps in NPN transistors were measured by deep level transient spectrum (DLTS) before and after irradiation. The radiation will increase the trap densities and alter the energy level of the traps for the unhardened devices. By comparing the DLTS results of hardened and unhardened devices, it is found that there are great differences in their native traps. The energy level of the traps in the hardened devices is farther away from the center of the band gap than the unhardened devices. It may implies that the radiation hardness of the device can be achieved by improving the native trap states of the device.

Aiming at the significant needs of flexible DC converter valve applications in high-altitude areas, we investigate the effect of atmospheric neutrons on the failure rate of key core power devices in three kinds of converter valves, namely IGBTs, thyristors, and diodes. The safe working voltage boundary of the devices is obtained, and the failure rate caused by atmospheric neutrons in the real working environment of the power devices is calculated according to the results of the ground-accelerated irradiation test of atmospheric neutrons and the atmospheric neutron environment under the actual working conditions. The test results show that the failure rate of IGBTs, thyristors, and diodes caused by atmospheric neutrons is greatly affected by the blocking voltage, and the larger the blocking voltage is, the higher the failure rate of the device is. The research results can provide a basis for the design of the operating voltage of key core power devices of flexible DC converter valves and guide the evaluation of the failure rate and engineering design of the electronic system of DC ultra-high-voltage power transmission and transformation converter stations in the high-altitude environment of the Qinghai-Tibet Plateau. [ABSTRACT FROM AUTHOR]

Based on the test site at the Qinghai�Tibet Plateau with an altitude of 4 300 m, atmospheric neutron single event effects of a 65 nm high�speed large�area static random access memory (SRAM) array were measured in real�time. By breaking through key technologies such as effect screening, intelligent remote measurement and control, a total of 39 single�event upset were observed during the 153 d test period, of which multiple�cell upset (MCU) accounts for 23%, and the largest MCU is 9 bits. The contribution ratios of high�energy neutron, thermal neutron and alpha particle were analyzed in detail, and based on the multi�ground neutron flux data, the single�bit upset (SBU) and MCU failure in time (FIT) at Beijing ground and 10 km high�altitude application were deduced. It is found that the main cause of soft error on the ground is the alpha particle. As the altitude increases, the contribution of atmospheric neutron to soft error increases significantly. All MCUs are caused by high�energy neutron, and the MCU FIT value at an altitude of 10 km in Beijing is obviously increased. Its proportion increases from 8% of the ground to 26%. In combination with the device layout, an in�depth analysis of the MCU generation mechanism was carried out. Finally, a goal�oriented optimization method of memory soft error hardening strategy was proposed.

Single-Event Burnout (SEB) can cause hard damage to devices, leading to permanent failure. However, previous studies have rarely explored the effects of high-energy proton irradiation-induced SEB in β-Ga2O3 Schottky Barrier Diode (SBD), and the underlying mechanisms remain largely unexplored. Experimental results indicate that the reverse bias voltage during irradiation is a critical factor influencing the failure of β-Ga2O3 SBD. Compared to 300 MeV proton irradiation without bias, the introduction of a 300 V reverse bias voltage results in a significant reduction in forward current density (JF). When the reverse bias voltage reaches 400 V or higher, the 300 MeV proton induces SEB in the device. The SEM image of the damaged region reveals that the irradiated device has "voids" formed due to the melting of the Ga2O3 material. Geant 4 and TCAD simulation results indicate that the burnout phenomenon is caused by the elevated lattice temperature inside the device, which results from the implantation of secondary particles under a high reverse bias voltage. As the reverse bias voltage increases, the maximum lattice temperature of β-Ga2O3 SBD also rises. When the reverse bias voltage is sufficiently high, the local lattice temperature inside the device reaches the melting point of Ga2O3 material, ultimately leading to SEB. [ABSTRACT FROM AUTHOR]

This paper investigates the temperature-dependent effects of gamma-ray irradiation on β-Ga2O3 vertical Schottky barrier diodes (SBDs) under a 100 V reverse bias condition at a total dose of 1 Mrad(Si). As the irradiation dose increased, the radiation damage became more severe. The total ionizing dose (TID) degradation behavior and mechanisms were evaluated through DC, capacitance–voltage (C-V), and low-frequency noise (LFN) measurements by varying irradiation, and the test results indicated that TID effects introduced interface defects and altered the carrier concentration within the material. The impact of TID effects was more pronounced at lower temperatures compared to higher temperatures. Additionally, the annealing effect in the high-temperature experimental conditions ameliorated the growth of interface trap defects caused by irradiation. These results suggest that compared to low-temperature testing, the device exhibits higher TID tolerance after high-temperature exposure, providing valuable insights for in-depth radiation reliability studies on subsequent related devices. [ABSTRACT FROM AUTHOR]

Surface α-particle emissivity testing and spectral characterization of two leaded tin spheres (Sn10%Pb90%, Sn63%Pb37%) and one lead-free tin sphere (Sn96.5%Ag3.0%Cu0.5%, SAC305) were carried out. The results show that Sn10%Pb90% Sn spheres have the highest α-particle emissivity; Sn63%Pb37% Sn spheres are the next highest, which is an order of magnitude lower than the α-particle emissivity of Sn10%Pb90% Sn spheres; and SAC305 Sn spheres have the lowest emissivity, which is reduced by about 55.6% compared to the emissivity of Sn63%Pb37% Sn spheres. All three types of tin spheres, after purification treatment, achieved the grade of ultra-low alpha particle emissivity (<0.002 α/(cm2·h)). The internal radionuclide traceability of the tin sphere, combined with the energy spectrum, reveals that the emission spectrum of the tin sphere exhibits an obvious "single peak" characteristic, with the peak energy in the interval of 5 MeV~5.5 MeV. Comparative analyses revealed that 210Po is the main nuclide that produces alpha particles, and 210Po originates from the decay of 210Pb. Further Monte Carlo simulations show that α-particles with energies greater than 4.1 MeV in the measured energy spectrum all come from the contribution of radionuclides within 5 μm of the surface layer of the tin sphere, which accounts for 60% of the total radioactivity. Combining the experimental and simulation results, it is found that the internal radionuclides of the tin sphere are characterized by more surface layer and less internal layer. The above results are of great significance for the establishment of α-particle mitigation methods for tin spheres. [ABSTRACT FROM AUTHOR]

In this article, the effects of high-energy proton irradiation on top-gate graphene field-effect transistors (GFETs) were investigated by using 20 MeV protons. The basic electrical parameters of the top-gate GFETs were measured before and after proton irradiation with a fluence of 1 × 1011 p/cm2 and 5 × 1011 p/cm2, respectively. Decreased saturation current, increased Dirac sheet resistance, and negative drift in the Dirac voltage in response to proton irradiation were observed. According to the transfer characteristic curves, it was found that the carrier mobility was reduced after proton irradiation. The analysis suggests that proton irradiation generates a large net positive charge in the gate oxide layer, which induces a negative drift in the Dirac voltage. Introducing defects and increased impurities at the gate oxide/graphene interface after proton irradiation resulted in enhanced Coulomb scattering and reduced mobility of the carriers, which in turn affects the Dirac sheet resistance and saturation current. After annealing at room temperature, the electrical characteristics of the devices were partially restored. The results of the technical computer-aided design (TCAD) simulation indicate that the reduction in carrier mobility is the main reason for the degradation of the electrical performance of the device. Monte Carlo simulations were conducted to determine the ionization and nonionization energy losses induced by proton incidence in top-gate GFET devices. The simulation data show that the ionization energy loss is the primary cause of the degradation of the electrical performance. [ABSTRACT FROM AUTHOR]

Electron traps in AlGaN/GaN high electron mobility transistors were studied by combining theoretical and experimental methods. Energy levels about EC-0.9 eV due to irradiation are identified by deep-level transient spectroscopy (DLTS). Two electron traps, H1 (EC-0.63 eV) and H2 (EC-0.9 eV), were observed in the DLTS spectra. H1 was produced in device or material manufacturing, and H2 was caused by displacement damage. First, we reported that the signal peak of H2 can contribute from three defects labeled H2-1, H2-2, and H2-3 with energies EC-0.77 eV, EC-0.9 eV, and EC-0.98 eV, respectively. According to defect migration temperature and first principles calculation results, it is found that different configurations of di-nitrogen vacancy structures are the source of EC-0.77 eV and EC-0.9 eV signals. The defect of EC-0.98 eV is more stable at high temperatures, which may be related to gallium vacancy. [ABSTRACT FROM AUTHOR]