Balancing Hole and Electron Conduction in Ambipolar Split-Gate Thin-Film Transistors

Abstract

Complementary organic electronics is a key enabling technology for the development of new applications including smart ubiquitous sensors, wearable electronics, and healthcare devices. High-performance, high-functionality and reliable complementary circuits require n- and p-type thin-film transistors with balanced characteristics. Recent advancements in ambipolar organic transistors in terms of semiconductor and device engineering demonstrate the great potential of this route but, unfortunately, the actual development of ambipolar organic complementary electronics is currently hampered by the uneven electron (n-type) and hole (p-type) conduction in ambipolar organic transistors. Here we show ambipolar organic thin-film transistors with balanced n-type and p-type operation. By manipulating air exposure and vacuum annealing conditions, we show that well-balanced electron and hole transport properties can be easily obtained. The method is used to control hole and electron conductions in split-gate transistors based on a solution-processed donor-acceptor semiconducting polymer. Complementary logic inverters with balanced charging and discharging characteristics are demonstrated. These findings may open up new opportunities for the rational design of complementary electronics based on ambipolar organic transistors.

Negative Transconductance Heterojunction Organic Transistors and their Application to Full‐Swing Ternary Circuits

“…To investigate the characteristics of electron injection when PTCDI‐C13 is not in direct contact with the electrode (i.e., DNTT is interposed between the electrode and PTCDI‐C13), we fabricated a device in which DNTT was interposed between PTCDI‐C13 and the source and drain electrodes (DNTT/PTCDI‐C13 ambipolar TR) ( Figure a). The DNTT/PTCDI‐C13 ambipolar TR exhibited V ‐shaped ambipolar transfer characteristics at V D = −50 and 50 V, which have typically been observed in previous studies of conventional ambipolar transistors . In the output characteristics, both p‐ ( V G < 0) and n‐type operation ( V G > 0) were observed (Figure b,c).…”

Ambipolar device simulation based on the drift-diffusion model in ion-gated transition metal dichalcogenide transistors

“…In single crystalline TMDs, such mid-gap states are absent. On the other hand, previous simulations on ion-gated organic transistors used a fixed capacitance induced by the ionic liquids 44,45 , which cannot include the variation of the capacitance due to the modification of the ion distribution by the source-drain bias voltage and the back action from the carriers in semiconductors. The general perspective of the ambipolar transport in MOSFETs has been discussed in ref.…”

Recent Advances in Ambipolar Transistors for Functional Applications

“…Unbalanced charge injection and carrier mobilities can make the switching bias of ambipolar transistors away from their desired value of half of the drain voltage (0.5 V DD ) and result in unnormal Z‐shaped electrical properties of CMOS inverters with reduced noise immunity, lowered DC gain and increased static energy dissipation; ii) symmetric electron and hole turn‐on voltages. Balanced threshold bias under individual p‐ and n‐channel can induce relatively small operation voltage and hence low power consumption; iii) relatively small off current and hence large on/off ratio under unipolar mode. Due to the inherent ambipolar characteristics of semiconducting materials (electrical current induced by holes augments before the current generated by electrons all passes away), the vast majority of ambipolar transistors are incapable of being completely switched off (without well‐defined off‐state), which finally gives rise to superabundant leakage and energy consumption, reduced gain values as well as decreased noise immunity .…”

“…Another viable means to tune ambipolar transistors into unipolar devices is using multiple gates (e.g., split‐gate and tri‐gate structures) to control the charge transport electrostatically and directly . This method can regulate the polarity of transistors after manufacture and is reversible after withdrawing the gate bias.…”