Abstract
In this paper, we present a systematic approach
to the characterization and modeling of amorphous Indium Gallium Zinc
Oxide (a-IGZO) thin-film transistors (TFTs), where the key parameters
are determined from the analysis of both
$I$
–
$V$
and
$C$
–
$V$
characteristics,
in a step-by-step fashion, without complex interdependences that may
affect the accuracy of the results. Flat band voltage
${V}_{\rm FB}$
and
carrier concentration
${n}_{\rm
FB}$
are extracted by a method we have previously
developed, validated here by applying it to simulated data. Next,
the density of deep gap states is extracted, followed by the determination,
by a new method, of the shallow donor concentration. The tail states
parameters are determined last, by matching the calculated
${n}_{\rm FB}$
to
the experimental one. Simulations are then performed without any adjustable
parameters. The approach is applied to the study of device to device
variations, indicating that the material is strongly compensated.
As for the analysis of Negative Bias under Illumination Stress (NBIS),
this work confirms that the effect is due to creation of a double
donor, with a shallow level close to the conduction band (positive
correlation energy). Oxygen vacancies are the likely candidates. These
defects are not detected in unstressed devices, where the characteristics
can be accurately simulated by incorporating donors with a single
shallow level.
© 2014 IEEE
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