Surface Potential Visualization in Organic Antiambipolar Transistors Using Operando Kelvin Probe Force Microscopy for Understanding the Comprehensive Carrier Transport Mechanism

Abstract

Abstract An antiambipolar transistor (AAT) exhibits a negative differential transconductance (NDT) due to a partially overlapped p–n junction formed in the transistor channel. However, the NDT origin remains unclear. In this study, the operando Kelvin probe force microscopy is employed to unveil this issue. When the AAT is turned on, steep potential drops induced by pinch‐off states are visible in the p‐ and n‐type channels. Due to the similarity to the surface potential profiles in the constituent transistors, it is revealed that the pinch‐off points are formed at both edges of the p–n‐stacked layers. This result indicates that the overlapped layers behave like a pseudo‐drain electrode for both transistor channels. Therefore, the AAT drain current can be explained as the overlapped currents in the saturation regions of the p‐ and n‐type transistors. Moreover, the drain current is suppressed when either the p‐ or n‐type channel is completely depleted. The depletion layer formation is responsible for the NDT property. This technique provides a comprehensive understanding of the carrier transport mechanism of AATs, leading to the further evolution of organic electronic circuits.

Keywords

• carrier transport mechanism
• Kelvin probe force microscopy
• negative differential transconductance
• operando observation
• organic antiambipolar transistors