Electrical Properties of Intact Metal/Semiconductor Contact Formed with Graphene Insertion Layer

Abstract

It is known that atoms can hardly penetrate a graphene layer due to the densely-spreading electron wave function inside the honeycomb lattice of graphene. In this work, we report the systematic experimental studies demonstrating that a graphene layer inserted at metal/semiconductor interface is efficient to explore interface Fermi-level pinning effect. It is confirmed that the atomic impermeability of an inserted graphene layer prevents material inter-mixing to form an compositionally-abrupt Schottky contact. In case of metal/graphene/Si junction, the Schottky barrier shows a very weak dependence on metal work-function, implying that the metal Fermi-level is almost completely pinned at charge neutrality level on the surface of Si substrate [1]. The formation of small-size silicide patches, supplying electrical leakage paths, is considered to be blocked efficiently with the graphene insertion layer so that the strong Fermi-level pinning predicted theoretically can be explored in ideal circumstances (Figure 1). For metal/graphene/GaAs junction, the counter-intuitive negative Fermi-level pinning effect is observed, which is supported by the Schottky barrier decreasing as metal work-function increasing in the current-voltage characteristics of junction. This unusual negative Fermi-level pinning is found to occur on the small patches of GaAs surface with low interface-trap density where the normal weak Fermi-level pinning is expected. The finite-element electrostatic modeling indicates that the electric dipole layer due to the shift of bonding electrons (chemical interaction) at metal/graphene interface [2] can induce the negative Fermi-level pinning effect. The chemical interaction dipole layer and the work-function difference between metal and graphene determine combinedly the profile of electrostatic potential across the metal/graphene interface. Our work provides a reliable experimental method to form an atomically-sharp intact Schottky contact on any arbitrary semiconductor substrate, which will be an essential requirement for exploring the electrical properties of Schottky contact determined by the surface states of semiconductor substrate in unambiguous manners.

Reference [1] Hoon Hahn Yoon, Sungchul Jung, Gahyun Choi, Junhyung Kim, Youngeun Jeon, Yong Soo Kim, Hu Young Jeong, Kwanpyo Kim, Soon-Yong Kwon, and Kibog Park*, Nano Letters 17(1), 44 (2017) [2] P. A. Khomyakov, G. Giovannetti, P. C. Rusu, G. Brocks, J. van den Brink, P. J. Kelly, Physical Review B 79, 195425 (2009)

Acknowledgement This work was supported by Space Core Technology Development Program (2016M1A3A3A02017648), Basic Science Research Program (2016R1A2B4014762), and Global Ph.D Fellowship Program (2015H1A2A1033714) through the National Research Foundation funded from the Ministry of Science and ICT in Korea.