Nanowire size dependence on sensitivity of silicon nanowire field-effect transistor-based pH sensor

In this study, we investigated the effects of nanowire size on the current sensitivity of silicon nanowire (SiNW) ion-sensitive field-effect transistors (ISFETs). The changes in on-current (I _on) and resistance according to pH were measured in fabricated SiNW ISFETs of various lengths and widths. As a result, it was revealed that the sensitivity expressed as relative I _on change improves as the width decreases. Through technology computer-aided design (TCAD) simulation analysis, the width dependence on the relative I _on change can be explained by the observation that the target molecules located at the edge region along the channel width have a stronger effect on the sensitivity as the SiNW width is reduced. Additionally, the length dependence on the sensitivity can be understood in terms of the resistance ratio of the fixed parasitic resistance, including source/drain resistance, to the varying channel resistance as a function of channel length.