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69
Eq. 27
Unless algorithm optimisation is enabled (see below), the resulting gate-voltage
dependent mobility are plotted and saved with no further data validation. As for the
partition method, the maximum of
is flagged as the DUT reference mobility.
The threshold voltage is calculated as the
x
-intercept of the tangent curve to the maximum
of the derivative
.
Tip:
Derivative method allows the most detailed gate-voltage dependent mobility; however,
it is also the less robust against noise.
3.
Linear Fit Method
computes the linear fit for the whole experimental data set I
DS,i
(V
GS,i
), and
returns the mobility -with the associated threshold voltage- as a single, gate-voltage
independent value
.
The threshold voltage is calculated as the x-intercept of the linear fit.
Tip:
Use the
Fit Optimisation
options, see below, to exclude I
DS,i
(V
GS,i
) data that do not
comply with the linear fit requirements. Refer to
Mobility Computation
for a review of the
validity conditions for the linear fit algorithm.
Threshold Voltage
specifies the threshold voltage extrapolation method. The available options are:
1.
Linear Fit Extrapolation
It calculates
V
Th
according to the selected mobility computation
method, see the description of
Computation Method
controls above.
2.
Second Derivative
V
Th
is calculated as the V
GS
at which the second derivative of the drain
current -with respect to the gate voltage- is maximum, i.e.
Eq. 28
3.
IV Integration Method
is not currently available for OFET/TFT.
On Current
ring selector is used to specify at which gate voltage the ON current I
ON
must be read.
The ON current is the I
DS
current output at which the DUT can be considered fully ‘ON’. As such, this
value is intrinsically not well-defined and the ON gate voltage is arbitrarily selected. As a rule of
thumb, any voltage
V
GS
such that
V
GS
>>
V
Th
is acceptable as V
ON
. It is common practice, however, to
use the larger (in absolute value)
V
GS
swept as
V
ON
.
To automatically use
V
GS End
as
V
ON
, select the
At Max V_DS
option from the drop-down menu of the
ON current
ring selector. To select a different value for I
ON
, select the
User
option instead and the
enter
V
ON
using the V
ON
input.
