Heavy ion-induced electrical degradations and mechanisms of high-electron-mobility transistors (HEMTs) were investigated in this article. AlGaN/GaN HEMTs were irradiated by 800-MeV Bi ions with total fluence of 5.23×10 ¹⁰ ions/cm ² . The results show that the saturation current decreased by 13.1%, the threshold voltage negatively shifted by 0.21 V, the peak transconductance decreased by 26.6%, the reverse gate-leakage current increased much more than 16 times, and forward gate-leakage current increased more than three times. Furthermore, all electrical performances experienced partial recovery after room temperature annealing (RTA) and 175 °C thermal annealing except gate-leakage current. To further explore the mechanism of gate-leakage degradation, AlGaN/GaN heterojunction wafers were exposed to 1400-MeV Ta ions with fluence of 6.86×107 ions/cm ² , and characterized by conductive atomic force microscope (CAFM) before and after the irradiation. The results show that the leakage current significantly increased in AlGaN material areas after the irradiation. Comparing the increase in gate leakage of the AlGaN/GaN heterojunction and AlGaN/GaN HEMT induced by heavy ions irradiation, it can be seen that the gate-leakage current of AlGaN/GaN HEMT after heavy irradiation almost entirely was caused by latent tracks. The mechanism for the irreversible increase in gate leakage after heavy ions irradiation could be attributed to the latent tracks along the ion trajectories through the heterojunction.

To explore the role of hydrogen in radiation degradation of AlGaN/GaN high-electron-mobility transistors (HEMTs), the performance degradation of the hydrogen untreated and pretreated devices is compared under the exposure of carbon ions. The energy of carbon ions is chosen as 7.6 MeV, and the maximum fluence reaches $4 \times 10^{12}$ cm ⁻² . By electrical character measuring, it is found that the positive shift of the threshold voltage and the decrease of the transconductance occur after to the irradiation. Hydrogen pretreatment accelerates the shift of threshold voltage and the decrease of the transconductance. The threshold voltage of the device is almost unchanged under 1-MeV electron irradiations. This means that the displacement damage leads to the shift of the threshold voltage. The height of Schottky barrier hardly changes in the hydrogen pretreated devices, showing that the ionization defects such as the formation of interface states under the gate are not the main cause of device degradation. Deep level transient spectrum (DLTS) results show that the irradiations cause the increase of gallium vacancies, and the hydrogen pretreatment inhibits its formation. According to the first principle calculation, the existence of hydrogen in GaN layer can reduce the formation energy of and the number of charges of the defects. It is speculated that hydrogen atoms participate in the evolution of radiation defects, which changes the types and number of defects in the devices.

Radiation-induced leakage current degradations for SiC power MOSFETs are investigated by ¹⁸¹ Ta ion irradiation. An ion flux-related leakage degradation is reported for the first time. It is manifested as a more significant leakage current under higher flux irradiation than that under low flux irradiation, even though the total fluence is the same. Emission microscope (EMMI) results show that more leakage paths are formed for high flux irradiation. The drain bias during irradiation is another key fact to affect the radiation-induced leakage degradation. The leakage only occurs when the drain bias is larger than 300 V for flux = 1000/cm $^{2}\cdot \text{s}$ irradiation. An interesting phenomenon is that although radiation-induced leakage is not observed at 200 V with ion flux of 1000/cm $^{2}\cdot \text{s}$ , leakage appears when the ion flux increases to 6000/cm $^{2}\cdot \text{s}$ . A multi-ion interaction theory is proposed to explain the above phenomenon. The mechanisms of these phenomena are also proved by TCAD simulations.

In the complex space radiation environment, space electronic devices are inevitably damaged by energetic particles, such as protons, leading to degradation of electrical performance. However, previous studies have rarely explored the effect of proton irradiation on the electrical properties of $\bm{\beta} $ -Ga $_{\text{2}}$ O $_{\text{3}}$ Schottky barrier diodes (SBDs), and the underlying mechanisms remain largely unexplored. This article investigates the effect of 300-MeV proton irradiation on the electrical properties of the $\bm{\beta} $ -Ga $_{\text{2}}$ O $_{\text{3}}$ SBD. The degradation mechanisms are evaluated through current–voltage ( I – V ), capacitance–voltage ( C – V ), and deep-level transient spectroscopy (DLTS) measurements. After 300-MeV proton irradiation with the influence of 1 $\times$ 10 $^{\text{13}}$ p/cm $^{\text{2}}$ , the SBD devices show significant reduc-tion in forward current density and breakdown voltage ( V $_{\text{\text{br}}}$ ). The degradation is related to the decrease in carrier concentration due to the generation of body defects in the epitaxial layer caused by proton irradiation. In addition, further DLTS measurement shows that the body defects induced by 300-MeV proton irradiation are deep energy level defects, energy level ( E $_{\textit{C}}$ – E $_{\textit{T}}$ ) increases from 0.758 to 1.345 eV, and the defect concentration increases from 1.08 $\times$ 10 $^{\text{13}}$ cm $^{-\text{3}}$ to 1.51 $\times$ 10 $^{\text{13}}$ cm $^{-\text{3}}$ .

The electrical characteristics and low-frequency noise (LFN) of AlGaN/GaN high-electron-mobility transistors (HEMTs) after 3-MeV proton irradiation up to a total dose of 5.0W1014 p/cm2 have been studied in this paper. The devices experienced a 14.6% decrease in saturation current, a 0.35V positive shift of the threshold voltage (Vth) and a significant decrease in reverse gate leakage current after 3-MeV proton irradiation. Extracted by the LFN method, the flat-band voltage noise power spectral density (SVfb) increases from 4.112W10-12 7Hz -1 to 5.603W10-12 7Hz -1, the trap density increases from 2.79W1017 to 3.84W1017 cm-3 7eV-1 after the radiation. The main degradation mechanism is considered to be the increase of negatively charged trap density in the channel, which depletes more electrons and reduces the carrier mobility in the channel 2-dimensional electron gas (2DEG). We also extracted the radiation-induced trapped charge density according to the theoretical calculation; the result is consistent with the LFN measurement.

The related recovery effect of hydrogen on AlGaN/gallium nitride (GaN) high-electron-mobility transistors (HEMTs) irradiated by high-fluence protons was investigated in this article. The results show that under the same temperature and time conditions, the recovery effect induced by thermal hydrogen annealing is better than that of ordinary thermal annealing. Compared with the ordinary thermal annealing, the high-fluence proton-irradiated device experienced a 65-mA additional increase in saturation current at the gate-to-source voltage (V _gs ) of 0 V, a 0.074-V additional negative shift of the threshold voltage, a more significant increase in reverse gate leakage current and better gate lag after the hydrogen treatment. The defect densities are extracted by the low-frequency noise method. It shows that the trap density decreases from 8.32 × 10 ¹⁷ to 6.84 × 10 ¹⁷ cm ^-3 ·eV ^-1 after ordinary thermal annealing and then decreases from 6.84 × 10 ¹⁷ to 3.85 × 10 ¹⁷ cm ^-3 ·eV ^-1 after hydrogen treatment of an irradiated AlGaN/GaN HEMT. The mechanism for the decrease of trap density after the hydrogen treatment could be attributed to the H-passivated defects in the structures of AlGaN/GaN HEMTs.