Sidewall Electrical Damage in β-Ga₂O₃ Rectifiers Exposed to Ga⁺ Focused Ion Beams

The energy and beam current dependence of Ga⁺ focused ion beam milling damage on the sidewall of vertical rectifiers fabricated on n-type Ga₂O₃ was investigated with 5-30 kV ions and beam currents from 1.3-20 nA. The sidewall damage was introduced by etching a mesa along one edge of existing Ga₂O₃ rectifiers. We employed on-state resistance, forward and reverse leakage current, Schottky barrier height, and diode ideality factor from the vertical rectifiers as potential measures of the extent of the ion-induced sidewall damage. Rectifiers of different diameters were exposed to the ion beams and the “zero-area” parameters extracted by extrapolating to zero area and normalizing for milling depth. Forward currents degraded with exposure to any of our beam conductions, while reverse current was unaffected. On-state resistance was found to be most sensitive of the device parameters to Ga⁺ beam energy and current. Beam current was the most important parameter in creating sidewall damage. Use of subsequent lower beam energies and currents after an initial 30 kV mill sequence was able to reduce residual damage effects but not to the point of initial lower beam current exposures.