Chia-Yu Chen

Development of IGZO TFTs and Their Applications to Next-Generation Flat-Panel Displays

Abstract Organic light‐emitting devices (OLEDs) have shown superior characteristics and are expected to dominate the next‐generation flat‐panel displays. Active‐matrix organic light‐emitting diode (AMOLED) displays, however, have stringent demands on the performance of the backplane. In this paper, the development of thin‐film transistors (TFTs) based on indium gallium zinc oxide (IGZO) on both Gen 1 and 6 glasses, and their decent characteristics, which meet the AMOLED requirements, are shown. Further, several display prototypes (e.g., 2.4” AMOLED, 2.4” transparent AMOLED, and 32” AMLCD) using IGZO TFTs are demonstrated to confirm that they can indeed be strong candidates for the next‐generation TFT technology not only of AMOLED but also of AMLCD (active‐matrix liquid crystal display).

Investigating the Drain-Bias-Induced Degradation Behavior Under Light Illumination for InGaZnO Thin-Film Transistors

This letter investigates the effect of gate/drain bias stress in InGaZnO thin-film transistors under light illumination and in a darkened environment. Drain current-gate voltage (ID-VG) as well as capacitance-voltage (C-V) transfer curves are measured to analyze the degradation behavior. The device characteristic exhibits a positively parallel shift after the gate/drain bias stress in the dark. On the other hand, the identical stress performed under light illumination leads to not only a negative shift but also a distortion of the C-V curve in the off state. Such phenomenon can be attributed to hole-trapping-induced barrier lowering near the drain side after illuminated bias stress.

Self-Heating-Effect-Induced Degradation Behaviors in a-InGaZnO Thin-Film Transistors

This letter investigates degradation behaviors induced by the self-heating effect for amorphous indium-gallium-zinc-oxide (IGZO) (a-IGZO) thin-film transistors (TFTs). Both the surrounding oxide and other thermal insulating material and the low thermal conductivity of the IGZO layer itself cause the self-heating effect in a-IGZO TFTs. The heated channel layer enhances threshold voltage shift, and the evolution of threshold voltage shift is found to be dominated by charge-trapping effect. Further verifications indicate that the degree of threshold voltage shift is dependent on stress power only, and a wider channel leads to more severe self-heating effect.

Self-heating enhanced charge trapping effect for InGaZnO thin film transistor

This paper investigates the degradation mechanism under self-heating stress for InGaZnO thin film transistor. The apparent positive threshold voltage (Vt) shift and on-current degradation indicate that the combination of trap states generation and electron trapping effect occur during stress. Furthermore, the asymmetric degradation behavior in the Id-Vg saturation measurement demonstrates that the trap states location is near the source side since the relative vertical electrical field is higher than drain side. Moreover, the Joule heating generated by self-heating operation can enhance electron trapping effect and cause larger Vt shift in comparison with the gate-bias stress.

Origin of self-heating effect induced asymmetrical degradation behavior in InGaZnO thin-film transistors

This letter investigates asymmetrical degradation behavior induced by the self-heating effect in InGaZnO thin-film transistors. Both the surrounding oxide and other thermal insulating material, as well as the low thermal conductivity of the InGaZnO layer itself, cause the self-heating effect in InGaZnO thin-film transistors. The heated channel layer enhances threshold voltage shift, and the evolution of threshold voltage shift is found to be dominated by charge-trapping effect. Moreover, a non-uniform distribution of channel carrier concentration leads to an uneven temperature distribution through the InGaZnO active layer and results in the asymmetrical degradation behavior after self-heating operation.

Systematic Investigations on Self-Heating-Effect-Induced Degradation Behavior in a-InGaZnO Thin-Film Transistors

This paper investigates degradation behavior induced by the self-heating effect for InGaZnO (IGZO) thin-film transistors (TFTs). Both the surrounding oxide and other thermal insulating materials, as well as the low thermal conductivity of the InGaZnO layer itself, cause the self-heating effect in InGaZnO TFTs. The heated channel layer enhances the threshold voltage shift, and the evolution of threshold voltage shift is found to be dominated by charge-trapping effects. Moreover, a nonuniform distribution of channel carrier concentration leads to an uneven temperature distribution throughout the IGZO active layer, which results in the asymmetrical degradation behavior after the self-heating operation. Further verifications indicate that the degree of the threshold voltage shift is only dependent on stress power, regardless of stress Vg, Vd, and channel length. Further, two-stage dependence of the threshold voltage shift on dynamic stress frequency is found.