Charlene Chen

Two-dimensional numerical simulation of radio frequency sputter amorphous In-Ga-Zn-O thin-film transistors

We reported on a two-dimensional simulation of electrical properties of the radio frequency (rf) sputter amorphous In–Ga–Zn–O (a-IGZO) thin-film transistors (TFTs). The a-IGZO TFT used in this work has the following performance: field-effect mobility (μeff) of ∼12 cm2/V s, threshold voltage (Vth) of ∼1.15 V, subthreshold swing (S) of ∼0.13 V/dec, and on/off ratio over 1010. To accurately simulate the measured transistor electrical properties, the density-of-states model is developed. The donorlike states are also proposed to be associated with the oxygen vacancy in a-IGZO. The experimental and calculated results show that the rf sputter a-IGZO TFT has a very sharp conduction band-tail slope distribution (Ea=13 meV) and Ti ohmic-like source/drain contacts with a specific contact resistance lower than 2.7×10−3 Ω cm2.

Density of States of a-InGaZnO From Temperature-Dependent Field-Effect Studies

Temperature-dependent field-effect measurements were performed on radio-frequency sputtered amorphous In-Ga-Zn-O thin film transistors (TFTs). We studied the effect of temperature on the TFT electrical properties. We observed that the field-effect mobility (mu) increases and the threshold voltage (V T) shifts negatively with temperature, while the current on-off ratio and subthreshold slope (S) remain almost unchanged. We also observed that the TFT drain current (ID) is thermally activated, and the relation between the prefactor (ID0) and activation energy (E a) obeys the Meyer-Neldel rule. The density of localized gap states (DOS) was then calculated by using a self-consistent method based on the experimentally obtained E a. The result shows good agreement with the DOS distribution calculated from SPICE simulations.

Amorphous In?Ga?Zn?O Thin Film Transistor Current-Scaling Pixel Electrode Circuit for Active-Matrix Organic Light-Emitting Displays

In this paper, we analyze application of amorphous In–Ga–Zn–O thin film transistors (a-InGaZnO TFTs) to current-scaling pixel electrode circuit that could be used for 3-in. quarter video graphics array (QVGA) full color active-matrix organic light-emitting displays (AM-OLEDs). Simulation results, based on a-InGaZnO TFT and OLED experimental data, show that both device sizes and operational voltages can be reduced when compare to the same circuit using hydrogenated amorphous silicon (a-Si:H) TFTs. Moreover, the a-InGaZnO TFT pixel circuit can compensate for the drive TFT threshold voltage variation (� VT) within acceptable operating error range. # 2009 The Japan Society of Applied Physics

a-InGaZnO thin-film transistors for AMOLEDs: Electrical stability and pixel-circuit simulation

— Inverted-staggered amorphous In-Ga-Zn-O (a-InGaZnO) thin-film transistors (TFTs) were fabricated and characterized on glass substrates. The a-InGaZnO TFTs exhibit adequate field-effect mobilities, sharp subthreshold slopes, and very low off-currents. The current temperature stress (CTS) on the a-InGaZnO TFTs was performed, and the effect of stress temperature (TSTR), stress current (ISTR), and TFT biasing condition on their electrical stability was investigated. Finally, SPICE modelling for a-InGaZnO TFTs was developed based on experimental data. Several active-matrix organic light-emitting-display (AMOLED) pixel circuits were simulated, and the potential advantages of using a-InGaZnO TFTs were discussed.

Crystalline In–Ga–Zn–O Density of States and Energy Band Structure Calculation Using Density Function Theory

The density of states (DOS) and energy band structure of crystalline In–Ga–Zn–O (c-IGZO) and the impact of point defects on its electronic structure are investigated by first-principles calculations based on the density function theory. The calculated DOS showed that the p-orbitals of the oxygen atoms mostly contribute to the valance band maximum (VBM) of c-IGZO. The conduction band minimum (CBM) is dominated by s-orbitals of the Zn/Ga mixture atoms, while the In atoms have the largest spatial spread of wave function. Oxygen vacancies create fully occupied defect states within the band gap and serve as deep donors. Both hydrogen substitutions and interstitials act like shallow donors, and raise the Fermi level above the CBM. Oxygen split interstitials created fully occupied defect states above VBM, while oxygen octahedral interstitials create both occupied and unoccupied states, and may serve as acceptors.

P-14: AM-OLED Pixel Circuits Based on a-InGaZnOThin Film Transistors

In this paper, we investigated the application of amorphous In-Ga-Zn-O (a-InGaZnO) thin film transistors (TFTs) to active-matrix organic light emitting display (AM-OLED) pixel circuits. SPICE model of a-InGaZnO TFTs was developed based on experimental data. Several pixel circuits were explored, and the potential advantages of using a-InGaZnO TFTs were discussed.