Abstract
We report theoretical study of the effects of energy relaxation on the tunneling current through the oxide layer of a two-dimensional graphene field-effect transistor. In the channel, when three-dimensional electron thermal motion is considered in the Schrödinger equation, the gate leakage current at a given oxide field largely increases with the channel electric field, electron mobility, and energy relaxation time of electrons. Such an increase can be especially significant when the channel electric field is larger than 1 kV/cm. Numerical calculations show that the relative increment of the tunneling current through the gate oxide will decrease with increasing the thickness of oxide layer when the oxide is a few nanometers thick. This highlights that energy relaxation effect needs to be considered in modeling graphene transistors.
Highlights
Graphene, a promising carbon-based electronic material, has been emerging as both a unique system for fundamental studies of condensed matter and quantum physics and a fascinating building block for integrated circuits in the age of post-silicon devices
Note that an electron temperature is well above the lattice temperature, and energy relaxation of the hot electrons can increase the tunneling current through the gate oxide. We report how this energy relaxation affects graphene field-effect transistors (FETs)
Because graphene is a 2D crystal, there is no band-structure in the tunneling direction which is perpendicular to the graphene plane
Summary
A promising carbon-based electronic material, has been emerging as both a unique system for fundamental studies of condensed matter and quantum physics and a fascinating building block for integrated circuits in the age of post-silicon devices. Two-dimensional graphene has a zero band gap and linear energy-momentum dispersion. Graphene’s linear energy − momentum dispersion causes its charge carriers to behave as massless Dirac fermions that can travel at a speed of 106 m s−1 [1]. The technical interest stems mostly from the fact that both carrier concentration and type (either electrons or holes) can be controlled by an applied field and that the carriers possess exceptionally high mobility. Graphene exhibits remarkable room temperature mobility in the order of 20,000– 200,000 cm V−1 s−1 [2] and high carrier mobility even up to 42,000 cm V−1 s−1 was observed [3]. The values range from 10,000–15,000 cm V−1 s−1 for exfoliated
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