Observation of the Ambient Effect in BTI Characteristics of Back-Gated Single Layer Graphene Field Effect Transistors

In this paper, the ambient doping effect on negative/positive bias temperature instability (NBTI/PBTI) of single layer graphene field effect transistors (FETs) is investigated. In ambient air, the
$\Delta {\rm V}_{\rm th}$
of NBTI is comparable with that of PBTI under the same stress voltage at room temperature. The
$\Delta {\rm V}_{\rm th}$
of NBTI appears insensitive to temperature, while the
$\Delta {\rm V}_{\rm th}$
of PBTI increases significantly with rising temperatures, due to the thermally activated charging of ambient doped defects at the graphene/
${\rm SiO}_{2}$
interface. This effect also results in an abnormal recovery of NBTI. In an ambient vacuum, the
$\Delta {\rm V}_{\rm th}$
is much less than that in ambient air. In addition, the
$\Delta {\rm V}_{\rm th}$
of both NBTI and PBTI decreases substantially for higher temperatures in the vacuum. The adsorbed molecules are mainly responsible for the
$\Delta {\rm V}_{\rm th}$
under BTI stress and the back-gated graphene FETs in the air.