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Two-dimensional numerical simulation of radio frequency sputter amorphous In–Ga–Zn–O thin-film transistors
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10.1063/1.3234400
/content/aip/journal/jap/106/8/10.1063/1.3234400
http://aip.metastore.ingenta.com/content/aip/journal/jap/106/8/10.1063/1.3234400

Figures

Image of FIG. 1.
FIG. 1.

Proposed DOS model for -IGZO. and are conduction and valence band edge energies, respectively. Solid curves within the bandgap represent the exponentially distributed band-tail states , while the dash curve near the conduction band edge represents the Gaussian-distributed donorlike OV states .

Image of FIG. 2.
FIG. 2.

-IGZO TFT: (a) output and [(b) and (c)] transfer characteristics . Both experimental (○) and simulation data (solid line: Schottky contact; : Ohmic contact) are shown. Extracted threshold voltage , filed-effect mobility , and subthreshold swing are also indicated. Inset of (c): the 2D TFT structure used in simulation. This structure is further decomposed into smaller mesh structures for a finite element analysis.

Image of FIG. 3.
FIG. 3.

A zoom-in view of the simulated TFT structure near the drain electrode. The contour distribution of the free electron concentration within the -IGZO layer is shown. The -direction is parallel to the TFT channel length direction, while the -direction is perpendicular to the device surface. The arrow represents the vector data for current density at each mesh grid point, and the length of the arrow is proportional to the magnitude of the current density. (Bias condition: and .)

Image of FIG. 4.
FIG. 4.

Simulated distribution of (a) the free electron density and (b) the -direction current density at the center of the -IGZO TFT structure. The gate voltage was changed from −0.6 up to 20 V. The film thickness of -IGZO is 20 nm. Position represents the back-channel surface, while represents the interface between -IGZO and the gate insulator. (c) Simulated energy band bending diagram at the center of the -IGZO TFT structure. The electron quasi-Fermi level was used as a reference energy level for all simulation results . The gate voltage was changed from −2 up to 20 V. Closed symbols: conduction band edge energy ; open symbols: valence band edge energy .

Image of FIG. 5.
FIG. 5.

Simulated -IGZO TFT linear region transfer curves for both linear and semilogarithm scales for various values are shown. The experimental data (symbol: ○) are also shown.

Image of FIG. 6.
FIG. 6.

(a) Simulated -IGZO Fermi-level position vs gate voltage . The Fermi-level position is represented as , where and are the energies for the conduction band edge and the Fermi level, respectively. The inset indicates the probe point for this data, and it is located at the center of the TFT, near (0.5 nm away from) the -IGZO/ interface. The slight offset is to avoid the calculation discontinuity that might occur at the interface. (b) The and extracted from simulated -IGZO TFT transfer characteristics for various values. The experimental data (symbol: ○) are also shown. Dash lines are the model fitting curves based on Eq. (10), and the parameters used in the model are illustrated in the inset.

Image of FIG. 7.
FIG. 7.

Simulated free electron concentration , ionized acceptorlike states , and ionized donorlike states as a function of . All the concentration data are integrated values over all energy levels within the bandgap. The symbols represent for various values, while the solid and dash lines are and , respectively. Since the data for and are the same for different , only one data line is shown. The probe point is the same as indicated in the inset of Fig. 6(a).

Image of FIG. 8.
FIG. 8.

Simulated -IGZO TFT: (a) linear region transfer curves and (b) extracted from TFT transfer characteristics for various values. The experimental data (symbol: ○) are also shown.

Image of FIG. 9.
FIG. 9.

-IGZO TFT simulated linear region curves in (a) the linear scale and (b) the semilogarithm scale for various OV state peak values . Real experimental data (○) are also shown as reference.

Image of FIG. 10.
FIG. 10.

Simulated ionized donorlike state concentration and gate voltage as a function of the Fermi-level position for various OV state peak values . The probe point is the same as indicated in the inset of Fig. 6(a).

Image of FIG. 11.
FIG. 11.

-IGZO TFT simulated linear region curves in (a) the linear scale and (b) the semilogarithm scale for various OV state mean energies . Real experimental data (○) are also shown as reference.

Image of FIG. 12.
FIG. 12.

Simulated ionized donorlike state concentration and gate voltage as a function of the Fermi-level position for various OV state mean energies . The probe point is the same as indicated in the inset of Fig. 6(a).

Tables

Generic image for table
Table I.

Key simulation parameters and -IGZO TFT properties.

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/content/aip/journal/jap/106/8/10.1063/1.3234400
2009-10-28
2014-04-18
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Two-dimensional numerical simulation of radio frequency sputter amorphous In–Ga–Zn–O thin-film transistors
http://aip.metastore.ingenta.com/content/aip/journal/jap/106/8/10.1063/1.3234400
10.1063/1.3234400
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