Subthreshold regime has the optimal sensitivity for nanowire FET biosensors.

Nanowire field-effect transistors (NW-FETs) are emerging as powerful sensors for detection of chemical/biological species with various attractive features including high sensitivity and direct electrical readout. Yet to date there have been limited systematic studies addressing how the fundamental factors of devices affect their sensitivity. Here we demonstrate that the sensitivity of NW-FET sensors can be exponentially enhanced in the subthreshold regime where the gating effect of molecules bound on surface is the most effective due to the reduced screening of carriers in NWs. This principle is exemplified in both pH and protein sensing experiments where the operational mode of NW-FET biosensors was tuned by electrolyte gating. The lowest charge detectable by NW-FET sensors working under different operational modes is also estimated. Our work shows that optimization of NW-FET structure and operating conditions can provide significant enhancement and fundamental understanding for the sensitivity limits of NW-FET sensors.

纳米线场效应晶体管（NW - FETs）作为检测化学/生物物质的强大传感器正在兴起，它具有多种吸引人的特性，包括高灵敏度和直接电读出。然而，到目前为止，关于器件的基本因素如何影响其灵敏度的系统研究还很有限。在此我们证明，在亚阈值区域，NW - FET传感器的灵敏度可以呈指数级提高，在该区域由于纳米线中载流子的屏蔽减少，结合在表面的分子的门控效应最为有效。这一原理在pH值和蛋白质传感实验中都得到了例证，在这些实验中，NW - FET生物传感器的工作模式通过电解质门控进行了调节。还估算了在不同工作模式下工作的NW - FET传感器可检测到的最低电荷量。我们的工作表明，对NW - FET结构和工作条件的优化可以显著提高NW - FET传感器的灵敏度，并对其灵敏度极限提供基本的理解。