【Member Papers】Xi’an Jiaotong University --- The γ-Ray TID Effect and Irradiation Damage Recovery on β-Ga₂O₃/Al₂O₃ MOSCAPs

      Researchers from the Xi’an Jiaotong University have published a dissertation titled "The γ-Ray TID Effect and Irradiation Damage Recovery on β-Ga₂O₃/Al₂O₃ MOSCAPs" in IEEE Transactions on Electron Devices.

Project support

      This work was supported in part by the Joint Funds of the National Natural Science Foundation of China under Grant U23A20367 and in part by the National Natural Science Foundation of China under Grant 62204198.

Background

      Beat-gallium oxide (β-Ga₂O₃) material has garnered considerable research interest in the fields of power electronics and optoelectronic devices, for the remarkable properties, such as a high breakdown electric field strength of up to 8 MV cm⁻¹ and a large bandgap of 4.8–4.9 eV, which allows devices to operate reliably under challenging conditions, such as high voltage and high temperature. Additionally, due to the high displacement energies of Ga and O atoms β-Ga₂O₃-baseddevices are also suitable for applications in complex radiation environments, including outer space and nuclear industry. Currently, the radiation effects of high-energy protons, electrons, γ -rays, and neutrons on β-Ga₂O₃-based metal–oxide–semiconductor (MOS) devices and diode devices have been studied. Based on current reports, the oxide layer materials and interfaces significantly affect the electrical characteristics of β-Ga₂O₃-based MOS structures, and they are also more susceptible to radiation damage. However, previous studies on total ionizing dose (TID) effects have predominantly focused on defect behaviors in β-Ga₂O₃ semiconductor materials, with relatively less analysis on the impact of the oxide layer and the interface between the oxide layer and the β-Ga₂O₃ material. Therefore, further research is needed to analyze the effects of irradiation damage on β-Ga₂O₃-based MOS devices.

Abstract

      In this study, the impact of γ -ray total ionizing dose (TID) irradiation on the electrical performance of beta-gallium oxide (β-Ga₂O₃)/Al₂O₃ MOSCAPs was investigated, and a new irradiation damage recovery method was also proposed using the supercritical N₂O (SCN₂O) fluid postoxidation annealing (POA) process. After a cumulative γ -ray dose of 1.108 Mrad (SiO₂), the net carrier concentration (N_d) decreased by 28.7%, and the interface state density (D_it) increased from 4.41×10¹¹ to 5.12×10¹¹ eV⁻¹ cm⁻², according to the frequency-dependent capacitance-voltage (C–V) measurements. Meanwhile, the effective trapped charge density (N_eff) was reduced from −1.82×10¹² to −1.37×10¹² eV⁻¹ cm⁻², leading to a decreased flat-band voltage (V_fb), which was attributed to the formation of positively charged oxide trapped charge (N_ot). What is more, the forward leakage current density increased by ten times, and a 9.5% decrease in the breakdown voltage (V_br) was observed according to the current-voltage (I–V) measurements. Moreover, the leakage current analysis indicated that the changes in the I–V characteristics were primarily caused by variations in D_it and N_ot. In addition, after the SCN₂O POA process at 120 °C, the damages of the irradiated device can be repaired. Specifically, the material properties, such as N_d, D_it, and N_eff, and the electrical properties of V_br and the forward leakage current density recovered to the preirradiation level. The results demonstrated that the low-temperature SCN2O POA process is promising for repairing TID irradiation damage in β-Ga₂O₃/Al₂O₃⋅ devices.

Conclusion

      In this study, the impact of 1.108-Mrad (SiO₂) γ -ray irradiation on the electrical performance of β-Ga₂O₃/Al₂O₃ MOSCAPs was investigated, and a novel low-temperature SCN₂O POA was proposed to repair irradiation-induced damage. After irradiation, N_d decreased by 28.7%, and D_it increased from 4.41 × 10¹¹ to 5.12 × 10¹¹ eV⁻¹ cm⁻². Neff decreased from −1.82 × 10¹² to −1.37 × 10¹² eV⁻¹ cm⁻², attributed to the formation of Not and led to a decreased V_fb. What is more, the leakage current density increased by ten times and a 9.5% decrease in V_br. The leakage current analysis indicated that irradiation-induced traps and charges were the primary causes of the reduction in V_br and the increase in the leakage current of the MOSCAPs. Besides, after SCN₂O POA, the material properties and the electric properties trended to recover to the preirradiation states, demonstrating that SCN₂O POA was useful for repairing the TID radiation effects in the β-Ga₂O₃/Al₂O₃ MOSCAPs. Specifically, N_d, D_it, and Neff of the irradiated material recovered to 2.36 × 10¹⁶ cm⁻³, 4.40 × 10¹¹ eV⁻¹ cm⁻², and −2.15 × 10¹² eV⁻¹ cm⁻², respectively, as the preirradiation state. Moreover, the leakage current, influenced by radiation-induced defects and traps, was governed by the PF mechanism at lower electric fields and by the TAT mechanism at higher fields. In short, these findings provide valuable insights into the repair of irradiation-induced damage and the enhancement of β-Ga₂O₃-based MOS devices for radiation environments. In the future, the SCF will be introduced into the Ga₂O₃-based device design and preparation in a more targeted way to enhance the radiation resistance.