Properties and applications of RuO2/GaN and related Schottky contacts

RuO₂/GaN and related materials were investigated as Schottky contacts in GaN-based photo-receiving and electronic devices. It was demonstrated that an RuO₂ film forms a stable Schottky contact on a GaN layer with a barrier height (φ_B) of 0.93 eV and transmittance of 70% in the visible and near UV region. The RuO₂/GaN Schottky diode showed a breakdown at over -50 V and leakage current of only 0.3 nA at -5 V. The RuO₂/GaN Schottky-type photodetector also exhibited a UV/Visible rejection ratio of over 3×10⁶ and responsivity of 0.23 A/W at 330 nm. The RuO₂ gate AlGaN/GaN HFET exhibited a high drain current (I_d)of 689.3 mA/mm and high transconductance (g)of 197.4 mS/mm. The cut-off frequency (f₁) and maximum oscillation frequency (f_max) were 27.0 GHz and 45.5 GHz, respectively.