Indexed on: 24 Dec '18Published on: 21 Dec '18Published in: Applied physics letters
Applied Physics Letters, Volume 113, Issue 25, December 2018. We have investigated the effect of crystalline structures on the thermal stability and electrical properties of nickel monogermanide (NiGe)/Ge contacts. The crystalline structure of the NiGe layer was found to be a determining factor for the thermal stability. Compared with the polycrystalline NiGe layer, the epitaxial NiGe layer with the orientation NiGe(100) ǁ Ge(110) exhibited a promising thermal stability due to its uniform interface and small residual stress. We have also demonstrated the alleviation of Fermi level pinning (FLP) by controlling the crystalline structures of NiGe layers on Ge(110) substrates. These works give us a hint that controlling the crystalline structure of metal layers enables one to control the Schottky barrier height of metal/Ge contacts, and the origin of FLP is not due to the intrinsic factor, e.g., metal induced gap states, but due to the extrinsic factors such as strong anisotropy of the work function and disorders at the metal/Ge interfaces.