Swift heavy ion irradiation-induced modifications in the electrical and surface properties of β-Ga2O3

The electrical device characteristics of Ni/β-Ga2O3 vertical Schottky barrier diodes (SBDs) were measured in situ during the irradiation of 120 MeV Ag7+ swift heavy ions (SHIs). These devices exhibit SHI irradiation-induced degradation with 120 MeV Ag7+ ions in the ion fluence ranges of 1 × 1010 to 1 × 1012 ions/cm2. The height of the Schottky barrier is found to decrease from 1.11 to 0.93 eV, and the ideality factor increases from 1.16 to 2.06. These changes indicate the degradation of the device with SHI irradiation. A significant four orders increase is observed in the leakage current density from 4.04 × 10−8 to 1.98 × 10−4 A/cm2 at −1 V, and the series resistance also increases from 3.38 × 103 to 1.15 × 104 Ω. X-ray photoelectron spectroscopy measurements show that the Ga ions are present in divalent and trivalent states with the spectral features having the binding energies centered at 20.2 eV and 19.9 eV (Ga 3d core-levels) before and after ion irradiation. The O 2s peak shifts to 23.7 eV, and there is an increase in intensity and peak broadening due to the change in the trivalent to divalent state of Ga due to the irradiation. The O(I) peak appears at 530.7 eV in the pristine sample with the Ga–O bonding with the Ga3+ state in pure Ga2O3. Moreover, there is a significant change in the intensity and the peak width of O(II) centered at 533.0 eV after ion irradiation at the fluence of 1 × 1012 ions/cm2. This indicates that there is an increase in the surface adsorbed/lattice oxygen, resulting in GaO.