Rhodium-based Schottky contacts on n-doped gallium nitride

Abstract

Electrical characteristics and thermal stability of Rhodium (Rh)-based Schottky contacts on n-GaN, including Rh/Au and Ni/Rh/Au, have been investigated and compared with those of the Ni/Au contact. Although the maximum Schottky barrier height (SBH) of the Rh/Au contact is slightly lower than that of Ni/Au, the inclusion of a thin Ni layer to yield the Ni/Rh/Au contact has led to a maximum SBH of 0.80 eV, surpassing that of Ni/Au by 0.07 eV and leading to a reduced reverse leakage current at -1 V by 1 order of magnitude compared to that of Ni/Au. The good performance of the Ni/Rh/Au contact can be attributed to the co-existence of Rh and a thin layer of Ni, which leads to limited adverse reaction of Ni with the GaN substrate, and formation of NiO and reduced interfacial defects at the metal/GaN interface. In addition, thermal stability studies have shown that Rh-based contacts exhibit better morphological stability than Ni/Au, and the Ni/Rh/Au contact has improved thermal stability over Rh/Au and Ni/Au contacts. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.