Performance of in situ oxidized platinum/iridium alloy Schottky contacts on (001), (2¯01), and (010) β -Ga2O3

Abstract

The performance of β-Ga2O3 Schottky contacts (SCs) fabricated using amorphous, intentionally oxidized platinum–iridium alloys was investigated as a function of alloy composition and β-Ga2O3 crystal orientation. PtyIr(1−y)Ox SCs with Pt fractions of y = 0.8, 0.5, and 0.3 were deposited on (001), (2¯01), and (010) single-crystal β-Ga2O3 substrates via the reactive rf and dc co-sputtering of Pt and Ir targets using oxygen–argon plasmas. In each case, the PtyIr(1−y)Ox SCs were highly rectifying with current rectification ratios (at ±3 V) of 11/10/9 orders of magnitude (at 300 K) for the (001)/(2¯01)/(010) β-Ga2O3 substrates. Current–voltage (I–V) and capacitance–voltage (C–V) measurements revealed that the Pt0.5Ir0.5Ox SCs contained the highest Schottky barriers on all β-Ga2O3 crystal faces, with the best contacts having ideality factors of 1.05 and image-force-corrected I–V and C–V determined barrier heights of 2.10 and 2.20 eV, respectively. These were consistently higher by ∼0.2 eV than the corresponding barriers for the Pt0.8Ir0.2Ox and Pt0.3Ir0.7Ox SCs, with the Pt0.5Ir0.5Ox SCs also having significantly lower reverse leakage currents (in the 0 to −100 V range). In comparison, the barrier heights of the best unoxidized plain-metal Pt0.5Ir0.5 SCs were only ∼1.2 eV, illustrating the effectiveness of in situ oxidation in improving the performance of PtIr SCs. All PtyIr(1−y)Ox SCs on (2¯01) β-Ga2O3 showed excellent high-temperature performance with rectification ratios (at ±3 V) of 109 at 300 °C and of 106 at 500 °C.