Chemistry Reference
In-Depth Information
mechanism to investigate the low-energy band structure, charge localization
and screening properties of bilayer graphene.
Fig. 1. (a) Schematic of graphene-transistor consisting of channel dimension
WL
.
(b) Schematic diagram of energy scale description of trapping-detrapping event where
the tunneling of carriers occurs mainly due to the trap states near the quasi-Fermi level
of graphene.
φ
B
is the height of tunneling barrier, the distance between the graphene
Fermi level and SiO
2
conduction band edge and
τ
(
x
) is the time constant associated
with the trapping event at a distance
x
from the graphene-SiO
2
interface.
2. The Correlated Number and Mobility Fluctuation Model
Oxide traps located at the SiO
2
and 2D electron interface are responsible
for low frequency noise in conventional MOSFETs. Among various models
proposed to explain 1
noise behaviors in MOS transistors, two most popu-
lar models are the number fluctuation and mobility fluctuation model. The
number fluctuation model, originally proposed by McWhorter,
48
arises due
to the tunneling transition between the oxide traps and MOSFET channel.
The other model is the mobility fluctuation model, based on Hooge's em-
pirical relationship
49
to fit the noise data for homogeneous semiconductor
and devices.
Due to the underlying similarity in device layout and operating prin-
ciple, we consider that noise in graphene-FET originates from both num-
ber and mobility fluctuations.
50
The number fluctuations are caused by
the tunneling of carriers to and from the interfacial oxide traps, while the
Coulomb scattering from the occupied oxide taps gives rise to the mobility
fluctuation in graphene channel.
Figure 1 shows the schematic of a graphene device consisting of channel
of dimension
/f
WL
.
For a carrier density of
n
, Drude conductivity
σ
=
neµ
=
µQ
n
, where total charge density
Q
n
=
en
. Hence the change in
σ
