Properties and applications of RuO/sub 2//GaN and related Schottky contacts

RuO/sub 2//GaN and related materials were investigated as Schottky contacts in GaN-based photo-receiving and electronic devices. It was demonstrated that an RuO/sub 2/ film forms a stable Schottky contact on a GaN layer with a barrier height (/spl phi//sub B/) of 0.93 eV and transmittance of 70% in the visible and near UV region. The RuO/sub 2//GaN Schottky diode showed a breakdown at over -50 V and leakage current of only 0.3 nA at -5 V. The RuO/sub 2//GaN Schottky-type photodetector also exhibited a UV/Visible rejection ratio of over 3/spl times/10/sup 6/ and responsivity of 0.23 A/W at 330 nm. The RuO/sub 2/ gate AlGaN/GaN HFET exhibited a high drain current (I/sub d/)of 689.3 mA/mm and high transconductance (g)of 197.4 mS/mm. The cut-off frequency (f/sub 1/) and maximum oscillation frequency (f/sub max/) were 27.0 GHz and 45.5 GHz, respectively.