Ion Irradiation-Induced Interface Mixing and the Charge Trap Profiles Investigated by In Situ Electrical Measurements in Pt/Al₂O₃/ β-Ga₂O₃ MOSCAPs

In situ <tex-math notation="LaTeX">I - V </tex-math> and <tex-math notation="LaTeX">C\!\!-\!\!V </tex-math> measurements were performed during the 120 MeV Au <tex-math notation="LaTeX">⁹⁺ </tex-math> ion irradiation on the Pt/Al <tex-math notation="LaTeX">_2O_3/β </tex-math> -Ga 2 O 3 , metal–oxide–semiconductor capacitors (MOSCAPs), to comprehend the swift heavy ion (SHI)-induced effects at the interface and in the device performance. At a maximum fluence of <tex-math notation="LaTeX">2× 10^12 </tex-math> ions/cm 2 , the <tex-math notation="LaTeX">I-\!V </tex-math> data showed a rise in the reverse leakage current by four orders of magnitude compared to the pristine device. The trap level (below the conduction band of Al 2 O 3) from Poole–Frenkel emission exhibits a variation from <tex-math notation="LaTeX">~ </tex-math> 1.1 to 0.91 eV. The conduction band offset <tex-math notation="LaTeX">(φ B) </tex-math> of Al <tex-math notation="LaTeX">_2O_3/β </tex-math> -Ga 2 O 3 changes from 1.48 to 1.25 eV as estimated under the Fowler–Nordheim tunneling mechanism. In situ <tex-math notation="LaTeX">C\!\!-\!\!V </tex-math> measurements show a significant shift in the flat band voltages and increased oxide in the border and interface due to charge trapping. The X-ray photoelectron spectroscopy (XPS) measurements of Al 2p and O 1s core levels revealed the pre-existing oxygen defects in Al 2 O 3 , which increase with fluence. The deconvoluted peaks of Al 2p at 74.6 eV designated to Al-sub oxide and the O 1s peak variation in the FWHM signifies the increase in the O defects. Cross-sectional transmission electron microscopy (XTEM) measurements on the irradiated device (at <tex-math notation="LaTeX">2× 10^12 </tex-math> ions/cm <tex-math notation="LaTeX">^2) </tex-math> revealed a modulated interface of Al <tex-math notation="LaTeX">_2O_3/β </tex-math> -Ga 2 O 3 and the formation of an interlayer of <tex-math notation="LaTeX">~ </tex-math> 4 nm Al x Ga y O z . The scanning transmission electron microscope (STEM)-based high-angle annular dark-field imaging (HAADF) energy-dispersive X-ray spectroscopy (EDS) mapping revelation and the depth profiles of XPS data confirm the formation of an Al x Ga y O z interlayer.