Direct Comparison of Ohmic Contact Properties of Graphene Versus Metal Source/Drain Electrodes by Fermi Level Modulation

초록

Two-dimensional (2D) van der Waals (vdW) atomic layered crystals have been extensively studied as a promising candidate for future electronics. Especially, graphene is a most famous 2D material which shows unique physical properties such as high mobility and gapless semiconductor, therefore, graphene has been studied in research area of contact engineering. [1-2] From these reasons, the graphene can be used as a metallic electrode for both n-type and p-type semiconductors to enhance the ohmic contact property at the Metal-Semiconductor junction by the fermi level modulation. In this work, we investigate MoS2 based field-effect transistors (FETs) with graphene as a source/drain (S/D) electrode which formed by using the direct-imprinting method. [3] In order to compare ohmic contact properties of graphene and metal electrodes on the same 2D vdWs semiconductor, we fabricated two graphene S/D electrodes on 2D vdWs semiconductor as a first group. After the electrical measurement, the graphene electrodes were fully covered by Ag metal electrodes which were used as S/D as a second group for direct comparison analysis. The first group of MoS2 FET, graphene as a S/D, showed excellent linear electron mobility of 50 cm2/Vs and high on/off current ratio of >106 due to its tunable ohmic property came from fermi level modulation. On the other hand, the second group showed poor electron mobility of 0.06 cm2/Vs and low on/off current ratio of 102