Thermally robust RuOx Schottky diodes and HEMTs on III‐nitrides

Abstract

AbstractThe potential usage of thermally robust RuOx Schottky contacts in III‐nitride‐based Schottky diodes and high electron mobility transistors (HEMTs) has been investigated. RuOx is deposited on nitride surface by sputtering Ru in Ar/O2 ambient. The influence of post sputtering annealing ambient and temperature on the characteristics of RuOx Schottky diodes on n‐type GaN on Si(111) substrate is addressed. We also report the comparative study of thermal stability between RuOx and Ni/Au Schottky diodes on InxAl1‐xN/GaN on Si(111) substrate in terms of the reverse bias leakage current and Schottky barrier height (SBH). RuOx contact shows a higher SBH of 1.24 eV and a lower leakage current of ∼10‐5 Acm‐2 (∼four orders of magnitude lower than that of Ni/Au) on InxAl1‐xN/GaN at –40 V after annealing at 800 oC in N2. In addition, RuOx Schottky gate HEMT on InxAl1‐xN/GaN on Si(111) substrate has shown a low gate leakage current of ∼6×10‐8 A/mm at ‐8 V after annealing at 700 oC in N2 for 1 minute. The lower gate leakage current has resulted in a transistor ON/OFF current ratio of ∼105. The maximum transconductance and ON‐resistance achieved by such HEMTs are about 0.18 S/mm and 8.33 Ωmm, respectively, for a gate length of 1.5 µm. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)