Hysteretic phenomena in GFET: Comprehensive theory and experiment

Abstract

We propose a comprehensive analytical theory for the description of versatile hysteretic phenomena in a graphene field effect transistor (GFET). Our theory account for the existence of the three most important rival factors, such as external dipoles on graphene free surface, localized states at the graphene-substrate interface, and the bound polarization charge coming from a ferroelectric substrate. In particular, we demonstrated that the absorbed dipole molecules (e.g., dissociated or highly polarized water molecules) can cause hysteretic form of carrier concentration as a function of gate voltage and corresponding dependence of graphene conductivity in GFET on the substrate of different types, including the most common SiO2 and ferroelectric ones. It was shown that the increase in the gate voltage sweeping rate leads to the complete vanishing of hysteresis for GFET on SiO2 substrate as well as for GFET on ferroelectric substrate for applied electric fields E less than the critical value Ec. For E > Ec, the cross-over from the anti-hysteresis to hysteresis take place. The carriers' trapping from the graphene channel by the interface states describes the “anti-hysteresis” in GFET on PZT substrate well enough. These results well correlate with the available experimental data up to the quantitative agreement. So, the obtained analytical results predict new and clarify existing effects in GFET. They describe quantitatively the physical principles of GFET operation and can become the first necessary step to transform the state-of-art from almost empirical to analytical level, because they can be directly applied to describe the basic characteristics of advanced non-volatile ultra-fast memory devices using GFET on versatile substrates.