Impact of Nickel Diffusion on Leakage Current Degradation in <i>β</i> ‐Ga ₂ O ₃ Schottky Barrier Diodes

ABSTRACT Beta‐phase gallium oxide ( β ‐Ga 2 O 3 ) is a promising ultra‐wide bandgap semiconductor for high‐power electronics, where the optimal selection of Schottky electrodes enables the achievement of elevated Schottky barrier heights and markedly enhanced device performance. This study investigates the impact of Ni diffusion on the leakage current in (100) β ‐Ga 2 O 3 Schottky barrier diodes (SBDs). Devices were fabricated using electron beam evaporation for Ni and Au Schottky contacts on unintentionally doped single crystals, with Ti/Au ohmic back contacts. Electrical measurements showed Ni‐SBDs exhibit higher reverse leakage current (−0.65 mA/cm 2 at −50 V) and lower Schottky barrier height (1.03 eV) compared to Au‐SBDs (−3.64 nA/cm 2 at −50 V) and (1.41 eV). Cross‐sectional corrected scanning transmission electron microscopy (CS‐STEM) and electron energy loss spectroscopy (EELS) revealed Ni diffusion at the interface of metal and β ‐Ga 2 O 3 , introducing oxygen vacancies that facilitate trap‐assisted tunneling and reduce barrier integrity. Emission microscopy (EMMI) localized leakage sites, which after KOH etching, corresponded to elongated etch pits. Geometric phase analysis (GPA) confirmed continuous strain beneath these pits. Magnetron‐sputtered Ni electrodes (Ni‐MS) amplified diffusion and defects, with voids as primary channels due to enhanced stress concentration. These results elucidate that Ni diffusion‐induced stress damage is the dominant mechanism for leakage under reverse bias, offering guidance for electrode optimization in β ‐Ga 2 O 3 power devices.