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

Abstract

Multivalued logic (MVL) computing could provide bit density beyond that of Boolean logic. Unlike conventional transistors, heterojunction transistors (H-TRs) exhibit negative transconductance (NTC) regions. Using the NTC characteristics of H-TRs, ternary inverters have recently been demonstrated. However, they have shown incomplete inverter characteristics; the output voltage (V_OUT ) does not fully swing from V_DD to G_ND . A new H-TR device structure that consists of a dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) layer stacked on a PTCDI-C13 layer is presented. Due to the continuous DNTT layer from source to drain, the proposed device exhibits novel switching behavior: p-type off/p-type subthreshold region /NTC/ p-type on. As a result, it has a very high on/off current ratio (≈10⁵ ) and exhibits NTC behavior. It is also demonstrated that an array of 36 of these H-TRs have 100% yield, a uniform on/off current ratio, and uniform NTC characteristics. Furthermore, the proposed ternary inverter exhibits full V_DD -to-G_ND swing of V_OUT with three distinct logic states. The proposed transistors and inverters exhibit hysteresis-free operation due to the use of a hydrophobic gate dielectric and encapsulating layers. Based on this, the transient operation of a ternary inverter circuit is demonstrated for the first time.