Modeling Radiation-Induced Degradation in Top-Gated Epitaxial Graphene Field-Effect-Transistors (FETs)

Abstract

This paper investigates total ionizing dose (TID) effects in top-gated epitaxial graphene field-effect-transistors (GFETs). Measurements reveal voltage shifts in the current-voltage (I-V) characteristics and degradation of carrier mobility and minimum conductivity, consistent with the buildup of oxide-trapped charges. A semi-empirical approach for modeling radiation-induced degradation in GFETs effective carrier mobility is described in the paper. The modeling approach describes Coulomb and short-range scattering based on calculations of charge and effective vertical field that incorporate radiation-induced oxide trapped charges. The transition from the dominant scattering mechanism is correctly described as a function of effective field and oxide trapped charge density. Comparison with experimental data results in good qualitative agreement when including an empirical component to account for scatterer transparency in the low field regime.

Effects of Proton and X-ray Irradiation on Graphene Field-Effect Transistors with Thin Gate Dielectrics

“…4. Furthermore, radiation-induced increases in oxide charge degrade carrier mobility due to Coulomb scattering [14], [18], contributing to the observed decrease in and The increase in with irradiation in the lower frequency range, -kHz, is likely due to increased trapping in the oxide layer, consistent with the increase in hysteresis and decrease in -slope following irradiation shown in Fig. 4.…”

“…The back-gated graphene field-effect transistors used in this study were fabricated at the Naval Research Laboratory NanoScience Institute using a process similar to the one described in [14]. The graphene films are transferred onto thermally grown on a silicon substrate, which serves as the global back gate.…”

“…Both mechanisms are likely contributing to the device radiation response immediately following X-ray irradiation [14]. as a function of frequency for devices before and after 2 Mrad( ) total dose irradiation, for V applied to the gate, and the source and drain grounded during irradiation.…”

“…While the gate oxide in graphene-based devices is certainly susceptible to radiation-induced charge trapping and interface trap buildup, which is behavior typical of conventional MOS systems [14], other mechanisms introduced by the interaction of radiation with environmental adsorbates or molecules in the graphene/ system can lead to a significant deviation from typical MOS radiation response [15]- [21]. Because graphene is a 2-D material, typically deposited in a few monolayers, the effects of trapped charges, defects, or even the separation distance between the graphene layer and underlying substrate can have a significant impact on device performance.…”

Carbon Nanoelectronics

“…Their numerical calculations predict the formation of sliding tunnel-coupled quantum dots resulting from the strong transverse electronic confinement of graphene nanoribbons. Aimed at employing graphene devices in radiation environments, Esqueda et al, experimentally and theoretically investigate total ionizing dose effects in top-gated epitaxial graphene field-effect transistors (GFETs) [16]. The research compliments and expands the growing body of experimental results pertaining to the radiation response of graphene and carbon nanotubes.…”