Photo-responsive MoS₂/organic-rubrene heterojunction field-effect-transistor: Application to photo-triggered ternary inverter

Multivalued logic (MVL) circuits with higher efficiencies, such as the ternary inverter, can be considered as promising structures to overcome the limitation of a binary system. Photo-responsive characteristics of the two-dimensional (2D) MoS₂ and the organic-rubrene nanosheet (NS) n-p heterojunction field-effect-transistor (FET) are studied with the aim to construct a novel photo-triggered ternary inverter as a MVL circuit. Anti-ambipolar transistor (AAT) characteristics were observed for the MoS₂/organic-rubrene-NS n-p heterojunction FETs. The serially connected devices comprising the AAT with a single MoS₂ (n-type)-based FET or with a single rubrene-NS (p-type)-based FET were fabricated to investigate inverter characteristics, which can be advantageous compared to the conventional complementary metal-oxide semiconductor employed in a binary logic circuit. Interestingly, the inverters employing the AAT connected to the p-type rubrene-NS-based FET in series were successfully operated as MVL circuits under light irradiation. The characteristics of new photo-triggered ternary inverters originate from the distinct photo-responsivity of p-type organic-rubrene-NS as well as the positive shift of the threshold voltage of the AAT and p-type rubrene-NS-based FET based on the photo-gating effect, achieved under specific light-irradiation conditions. In this work, a new photo-triggered (i.e. photo-driven) ternary inverter using 2D-MoS₂ and organic semiconducting rubrene-NS heterojunction FETs was successfully realized. The heterojunctions of 2D inorganic and organic semiconductors exhibit great potential toward the development of new photo-responsive MVL circuits and multifunctional transistors with extraordinary characteristics and performance including energy saving.