Complementary p- and n-Type Doping using Polymer Electrolyte Gates for Low-Power Graphene Inverters

Abstract

Graphene has extensively attracted great interest to replace Si-based electronics due to its outstanding electrical properties. However, ambipolar characteristics of graphene field-effect transistors (FETs) and low on/off current ratio due to the absence of bandgap in graphene are unfavorable for logic gates. In addition, conventional back-gated structure using SiO2 as a dielectric has a high operating voltage. To overcome this problem, several researchers have used top-gated device structure with high-k dielectrics. However, the use of high-k materials requires expensive and complex processes. In this regard, polymer electrolyte gating was successfully demonstrated in carbon nanotube and graphene FETs. Here, we report a low-power unipolar p- and n-type graphene FETs by using polymer electrolytes. For p- or n-type conduction in graphene, we selected a surface charge transfer doping method by using poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAA), respectively. Lithium perchlorate (LiClO4) known as a salt for electrolyte was added in PEI or PAA matrix to obtain high gate efficiency. We demonstrated the low-power graphene inverter with polymer electrolyte gates, which is compatible with the CMOS technologies. The maximum voltage gain is 1.11 at VDD = 1 V. This value is ~80 times higher than that of back-gated polymer-doped graphene inverter. This demonstration will be useful in the development of low-cost, low-power flexible electronic devices.