# Effect of Quasi-One-Dimensional Properties on Source/Drain Contacts in Vertical Nanowire Field-Effect Transistors (VNWFETs)

## TL;DR

This paper explores how the unique one-dimensional properties of nanowires affect contact resistances in vertical nanowire transistors.

## Contribution

The study reveals that radial contact resistance in nanowires is significantly higher than axial due to quantum confinement effects.

## Key findings

- Radial contact resistance in nanowires under 30 nm is much higher than axial resistance due to quantized energy levels.
- Increasing overlap length slightly reduces radial resistance but it remains higher than axial resistance.
- Quantum confinement in nanowires limits radial transport, impacting contact resistance.

## Abstract

In this study, we investigated the influence of quasi-one-dimensional (Quasi-1D) characteristics on the source and drain contact resistances within vertical nanowire (NW) field-effect transistors (FETs) of diminutive diameter. The top contact of the NW is segregated into two distinct regions: the first encompassing the upper surface, designated as the axial contact, and the second encircling the side surface, known as the radial contact, which is formed during the top-contact metal deposition process. Quantum confinement effects, prominent within Quasi-1D NWs, exert significant constraints on radial transport, consequently inducing a noticeable impact on contact resistance. Notably, in the radial direction, electron tunneling occurs only through quantized, discrete energy levels. Conversely, along the axial direction, electron tunneling freely traverses continuous energy levels. In a meticulous numerical analysis, these disparities in transport mechanisms unveiled that NWs with diameters below 30 nm exhibit a markedly higher radial contact resistance compared to their axial counterparts. Furthermore, an increase in the overlap length (less than 5 nm) contributes to a modest reduction in radial resistance; however, it remains consistently higher than the axial contact resistance.