Analytical measurements of contact resistivity in two-dimensional WSe<sub>2</sub> field-effect transistors
Inyong Moon, Min Sup Choi, Sungwon Lee, Ankur Nipane, James Hone, Won Jong Yoo
Abstract
Abstract It becomes clear that, in two-dimensional (2D) materials-based devices, sheet resistances underneath electrodes change due to a metallic contact, leading to substantial errors in determining a transfer length. Thus, the extraction of transfer length and corresponding contact resistivity must be revisited to assess the performance of 2D devices. In this study, we present the three different approaches of determining the contact resistivity in 2D WSe 2 field effect transistors for the first time by theoretical analysis using the resistive network model as well as electrical measurements using the contact-end resistance and transfer length methods, based on the followings: (a) contact resistance multiplied by transfer length ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>R</mml:mi> <mml:mrow> <mml:mrow> <mml:mtext>cf</mml:mtext> </mml:mrow> </mml:mrow> </mml:msub> </mml:mrow> <mml:mi>W</mml:mi> <mml:mo>⋅</mml:mo> <mml:mrow> <mml:msub> <mml:mi>L</mml:mi> <mml:mrow> <mml:mrow> <mml:mtext>Tk</mml:mtext> </mml:mrow> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> ), (b) integrated contact resistance ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mstyle displaystyle="true"> <mml:mrow> <mml:munderover> <mml:mo>∫</mml:mo> <mml:mn>0</mml:mn> <mml:mi>L</mml:mi> </mml:munderover> <mml:mrow> <mml:mi>R</mml:mi> <mml:mrow> <mml:mo>(</mml:mo> <mml:mi>x</mml:mi> <mml:mo>)</mml:mo> </mml:mrow> <mml:mo>⋅</mml:mo> <mml:mi>W</mml:mi> <mml:mtext>d</mml:mtext> <mml:mi>x</mml:mi> </mml:mrow> </mml:mrow> </mml:mstyle> </mml:mrow> </mml:math> ), and (c) contact resistance raised to a constant power <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msup> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi>R</mml:mi> <mml:mrow> <mml:mrow> <mml:mtext>cf</mml:mtext> </mml:mrow> </mml:mrow> </mml:msub> </mml:mrow> <mml:mi>W</mml:mi> </mml:mrow> </mml:mfenced> <mml:mi>α</mml:mi> </mml:msup> </mml:mrow> </mml:math> ). These different extraction methods give rise to almost identical transfer length and contact resistivity, validating our model and its accuracy from the results obtained by using various contact metals and plasma doping conditions. This work serves as a foundation for future research on the determination of physical parameters responsible for the carrier transport at the metallic contact interface in 2D semiconductor devices.