High quality Ru, Ir, Pd, Pt, Ag, and Au Schottky contacts (SCs) were fabricated on 2¯01 β-Ga2O3 single crystal substrates via rf sputtering under inert and oxidizing plasma conditions. The oxidized SCs exhibited significantly higher rectifying barriers and, with the exception of gold oxide, significantly improved high temperature performance, with more than 12 orders of magnitude of stable rectification at 180 °C. With the exception of Ag, the image-force-corrected laterally homogeneous barrier heights of the plain metal SCs were pinned close to 1.3 eV, irrespective of the metal work function, with the Fermi level at the SC interface close to the predicted VO (2+/0) transition level of fourfold coordinated oxygen vacancies. The equivalent barrier heights of the oxidized SCs were consistently 0.5–0.8 eV higher than their plain metal counterparts, lying in the range of 1.8–2.5 eV, with the increase attributed to the passivation of interfacial oxygen vacancies and a significant increase in the work function of the oxidized metals. The highest Schottky barriers for both the plain and oxidized metal SCs involved Ag, which may be linked to the relative ease of its unintentional and intentional oxidation, respectively. The very high rectifying barriers and the thermal stability of oxidized Schottky contacts to β-Ga2O3 indicate their potential for high temperature device applications.
Very high temperature operation β-Ga2O3 Schottky contacts were fabricated on moderately doped 2¯01 β-Ga2O3 single crystal substrates using four different types of intentionally oxidized platinum group metal (PGM) Schottky contacts (SCs), i.e., PtOx, IrOx, PdOx, and RuOx (x ∼ 2.0, 2.2, 1.1, and 2.4, respectively) formed by reactive rf sputtering of plain-metal targets in an oxidizing plasma. All four types of oxidized PGM SCs showed rectification ratios (at ± 3 V) of more than 10 orders of magnitude up to 300 °C, with almost no measurable increase in reverse leakage current density (Jrev) from that at room temperature. From 350 to 500 °C, a measurable increase in Jrev was observed, which was consistent with the thermionic emission of charge carriers over the respective image force (IF) lowered Schottky barriers. Despite this increase, PtOx(IrOx)[PdOx]{RuOx} SCs showed large rectification ratios (at ± 3 V) of 6 × 106(8 × 106)[5 × 105]{2 × 104} and IF-corrected barrier heights of 2.10(2.10)[1.90]{1.60} ± 0.05 eV, respectively, while operating at 500 °C. The significantly lower 500 °C barrier height of the RuOx SCs was due to the thermal reduction of RuOx to Ru that occurred above 400 °C. In contrast, the Schottky barriers of IrOx, PtOx, and PdOx SCs were thermally stable while operating at 500 °C, indicating significant potential for their use in very high temperature rectifying devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.