We evaluated the electrical characteristics of two different AlGaN/GaN high-electron mobility transistors (HEMTs) for the 5-MeV proton irradiation effects. The difference of the HEMTs originates from the isolation methods, such as mesa etching and nitrogen ion implantation. At a proton fluence of 1 × 10 ¹⁴ p/cm ² , the saturation drain currents of two devices are reduced by 50% and 11% for the mesa etching and the nitrogen ion implantation, respectively. The displacement damages are believed to degrade the electrical characteristics of AlGaN/GaN HEMTs. AlGaN/GaN HEMTs with nitrogen ion implantation isolation show relatively higher radiation hardness than those with mesa etching isolation. The reason is that plasma etching easily damages the surface of mesa sidewall and causes more defects by proton irradiation.

This paper presents a one-transistor dynamic random-access memory (1T-DRAM) cell based on a gate-all-around junction-less field-effect transistor (GAA-JLFET) with a Si/SiGe heterostructure for high-density memory applications. The proposed 1T-DRAM achieves the sensing margin using the difference in hole density in the body region between ‘1’ and ‘0’ states. The Si/SiGe heterostructure forms a quantum well in the body and reduces the band-to-band tunneling (BTBT) barrier between the body and drain. Compared with the performances of the 1T-DRAM with Si homo-structure, the proposed 1T-DRAM improves the sensing margin and retention time because its storage ability is enhanced by the quantum well. In addition, the thin BTBT barrier reduced the bias condition for the program operation. The proposed 1T-DRAM showed a high potential for memory applications by obtaining a high read current ratio at ‘1’ and ‘0’ states about 10⁸ and a long retention time above 10 ms.

The device performance deterioration mechanism caused by the total ionizing dose effect after the γ-ray irradiation was investigated in GaN-based metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) for a 5 nm-thick SiN and HfO₂ gate dielectric layer. The γ-ray radiation hardness according to the gate dielectric layer was also compared between the two different GaN-based MIS-HEMTs. Although HfO₂ has exhibited strong tolerance to the total ionizing dose effect in Si-based devices, there is no detail report of the γ-ray radiation effects in GaN-based MIS-HEMTs employing a HfO₂ gate dielectric layer. The pulsed-mode stress measurement results and carrier mobility behavior revealed that the device properties not only have direct current (DC) characteristics, but radio frequency (RF) performance has also been mostly degraded by the deterioration of the gate dielectric quality and the trapped charges inside the gate insulator. We also figured out that the immunity to the γ-ray radiation was improved when HfO₂ was employed instead of SiN as a gate dielectric layer due to its stronger endurance to the γ-ray irradiation. Our results highlight that the application of a gate insulator that shows superior immunity to the γ-ray irradiation is a crucial factor for the improvement of the total ionizing dose effect in GaN-based MIS-HEMTs.

TID effects occur in MOS-gated transistors in radiation environments where proton and gamma-rays irradiate the devices. TID effects seriously affect the electrical characteristics of Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET). They can eventually result in the malfunction of power systems when exposed to long-term radiation conditions. We irradiated gamma-rays and protons into 1.2 kV SiC MOSFETs and evaluated the change in electrical properties to analyze the TID’s effects. As a result of the experiment, the threshold voltage (V_T) and on-resistance (R_on) of 1.2 kV SiC MOSFETs decreased because positive fixed charges inside the oxide increased depending on the radiation dose of the gamma-ray and fluence of the proton irradiations. The degradation of breakdown voltage (BV) occurred owing to a change in the depletion curvature at the edge of termination regions owing to the trapping of the charge in the field’s oxide.

We evaluated the effect of the proton irradiation energy on the DC characteristics of AlGaN/GaN high electron mobility transistors (HEMTs). Devices were exposed to various irradiation energies, i.e., 0.5 MeV, 5 MeV, and 60 MeV, respectively, with a fluence of 1 × 10 ¹⁴ p cm ⁻² at room temperature. The 0.5 MeV-irradiated HEMT shows the largest degradation of transfer characteristics than other HEMTs because the lower proton energy has a larger non-ionizing energy loss (NIEL). The threshold voltage of HEMTs with 0.5 and 5 MeV proton irradiation is positively shifted due to the reduction of 2-dimensional electron gas (2DEG) density by defects created during irradiation. However, the 60 MeV-irradiated HEMT showed a negative shift of threshold voltage with no degradation of drain current. Also, the gate leakage current of fabricated HEMTs decreased with an increasing irradiation energy. These anomalous DC characteristics were expected due to the creation of a proton radiation-caused interfacial oxide layer between the gate and AlGaN layer.

This study investigated the combined effects of proton irradiation and surface pre-treatment on the current characteristics of Gallium Nitride (GaN)-based metal-insulator-semiconductor high-electron-mobility-transistors (MIS-HEMTs) to evaluate the radiation hardness involved with the Silicon Nitride (SiN) passivation/GaN cap interface. The impact of proton irradiation on the static and dynamic current characteristics of devices with and without pre-treatment were analyzed with 5 MeV proton irradiation. In terms of transfer characteristics before and after the proton irradiation, the drain current of the devices without and with pre-treatment were reduced by an increase in sheet and contact resistances after the proton irradiation. In contrast with the static current characteristics, the gate-lag characteristics of the device with pre-treatment were significantly degenerated. In the device with pre-treatment, the hydrogen passivation for surface states of the GaN cap was formed by the pre-treatment and SiN deposition processes. Since the hydrogen passivation was removed by the proton irradiation, the newly created vacancies resulted in the degeneration of gate-lag characteristics. After nine months in an ambient atmosphere, the gate-lag characteristics of the device with pre-treatment were recovered because of the hydrogen recombination. These results demonstrated that the radiation hardness of MIS-HEMTs was affected by the SiN/GaN interface quality.