Performance Improvement of (Al_<i>x</i>Ga_1–<i>x</i>)₂O₃/Ga₂O₃ Heterostructure FET via Supercritical Isostatic Pressing-Induced Self-Redox

Ultrawide-bandgap β-Ga₂O₃-based metal-oxide-semiconductor field-effect transistors (MOSFETs) are highly promising for ultrahigh-power applications due to their exceptional material properties. However, the performance of β-Ga₂O₃ MOSFETs is well below the theoretical limit of the materials, primarily constrained by intrinsic bulk defects in β-Ga₂O₃ and the lack of effective processing methods to enhance device performance. In this work, we designed and fabricated (Al_<i>x</i>Ga_1-<i>x</i>)₂O₃/Ga₂O₃ heterostructure FET and developed supercritical isostatic pressure carbon dioxide (SCIP-CO₂) technology to induce a self-redox reaction within the device under a three-dimensional isostatic pressure environment. Through self-oxidation and reduction, SCIP-CO₂ treatment effectively repairs dangling bonds, reducing defects within the materials to improve device performance. This process uses only the O atoms generated by the self-reducing reaction in the Ni and Al₂O₃ layers of the device to repair the defects, and no other substances are introduced. Following SCIP-CO₂ treatment, the devices exhibited a substantial increase in on-current, a reduction in the subthreshold swing (from 500 to 440 mV/dec), enhanced transconductance (from 15.9 to 24.3 μS), a decrease in the interface defect density from 6.5 × 10¹² to 2.4 × 10¹² cm^-2, and a marked reduction in gate leakage. This proves that SCIP-CO₂ treatment can further enhance device performance after the device has completed the fabrication process. The comprehensive optimization of the electrical performance of devices demonstrates the enormous potential of SCIP-CO₂ technology for next-generation power electronic devices.