In this work, the single-event burnout (SEB) mechanism of p-GaN gate AlGaN/GaN HEMTs has been studied systematically. The irradiation experiment was carried out based on Ta ions with high linear energy transfer of 75.4 MeV/(mg/cm2), a standard criterion for commercial space applications. It is clearly observed that both the drain current and gate current increase during the irradiation. With the increasing drain bias, the device burns out eventually. Technology computer-aided design simulation was used to explore the possible burnout mechanism. The local high electric field peak induced by the electron and hole redistribution was proposed to explain the permanent damage. When heavy ions impact the device, electron–hole pairs are formed. With the aid of a horizontal electric field across the channel, electrons and holes move toward the drain and gate, respectively. The accumulation of electrons and holes around the drain edge and gate edge induces the local high electric field, which is even higher than the intrinsic breakdown electric field of GaN and AlGaN. The scanning electron microscope results verified the proposed SEB mechanism. This research offers significant theoretical and experimental insights for evaluating the reliability of GaN power devices against high-energy single-event burnout in aerospace applications.

A high combination of transconductance (gm), current gain cutoff frequency (fT) and three terminal breakdown voltage was achieved using thin barrier AlGaN/GaN HEMTs and TiN-based source contact ledge. The sheet resistance is effectively reduced, whereas the peak extrinsic trans-conductance is improved by 24% from 334mS/mm to 415mS/mm. The thin barrier AlGaN/GaN HEMTs with TiN-based source ledge exhibit a maximum drain current of 1096mA/mm, an three-terminal off-state breakdown voltage (BVDS) of 151V, a high current-gain cutoff frequency fT of 69GHz, and a high power-gain cutoff frequency fMAX of 110GHz. No significant drain current collapse was observed on thin barrier AlGaN/GaN HEMTs with TiN-based source contact ledge. The uniform fT characteristic over a wide range of bias condition is achieved by using the TiN-based source contact ledge devices. The calculated Johnson’s figures of merit (J-FOM=BVGD×fT) is 10.4THz-V, which is the highest record so far for 0.2μm T-gate SiN passivation AlGaN/GaN HEMTs without source field plate (SFP).

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.

The electrical degradation in AlGaN/GaN high-electron-mobility transistors (HEMTs) is examined under irradiation with 7.6-MeV carbon (C), 20-MeV oxygen (O), and 30-MeV fluorine (F) ions in situ . To characterize the radiation damage in the HEMTs, the ionizing dose $D_{i}$ , displacement dose $D_{d}$ , and number of vacancies versus the chip depth in the devices have been calculated for heavy ions. As expected, in all three types of HEMTs, the output current decreases more than 30% and threshold voltage positive shifts after the irradiation fluence of $4\times 10^{12}$ ions/cm ² . The performance degradation of AlGaN/GaN HEMTs is caused by radiation-induced charged defects. Based on calculation and experimental results, it is shown that the nonionizing energy loss (NIEL) method is not suitable for estimating the degradation of AlGaN/GaN HEMTs either considering gallium vacancy or considering both gallium vacancy and nitrogen vacancy. In the same displacement damage dose, the threshold voltage degradation rate depends on the type of incident particles and independent of the channel length. The damage caused by carbon ions is the smallest and the damage caused by fluoride ions is the largest.

This paper reports the AlGaN/GaN/ Si δ -doped AlGaN/GaN:C HEMT device on silicon with high channel conductivity, high breakdown field (E-field) strength, and low current collapse by using the Si-doped AlGaN back barriers. The Si δ -doped AlGaN back barrier was used to compensate for the reduction of channel conductivity as a result of a carbon-doped semiinsulating GaN buffer layer. The maximum drain current increases from 412 to 720 mA/mm, and peak extrinsic transconductance is improved from 103 to 210 mS/mm. Due to the reduction of electric field between the gate and drain along the GaN channel by inserting the Si δ -doped AlGaN back barrier layer, it can effectively suppress the capture of electrons in channel by carbon-induced accepted traps in the GaN:C buffer. Combined with the high conductivity of Si δ -doped AlGaN back barrier and high resistance of GaN:C buffer, the device showed the high breakdown E-field strength and the low specific on-resistance. Our proposed device is observed to hold a gate-drain voltage of 769 V at 10 μA/mm (7-μm gate-drain spacing) and 0.53 mΩ · cm² and the gate-to-drain electric field corresponds to 1.1 MV/cm.