We present a qHD (960 × 540 with three sub‐pixels) top‐emitting active‐matrix organic light‐emitting diode display with a 340‐ppi resolution using a self‐aligned IGZO thin‐film transistor backplane on polyimide foil with a humidity barrier. The back plane process flow is based on a seven‐layer photolithography process with a CD = 4 μm. We implement a 2T1C pixel engine and use a commercial source driver IC made for low‐temperature polycrystalline silicon. By using an IGZO thin‐film transistor and leveraging the extremely low off current, we can switch off the power to the source and gate driver while maintaining the image unchanged for several minutes. We demonstrate that, depending on the image content, low‐refresh operation yields reduction in power consumption of up to 50% compared with normal (continuous) operation. We show that with the further increase in resolution, the power saving through state retention will be even more significant.
In this study, we investigate the effect of mechanical strain on the performance of flexible amorphous In–Ga–Zn–O (a-InGaZnO) thin-film transistors. Drain current–gate voltage (I
D–V
G) and capacitance–voltage (C–V) transfer curves are measured to analyze the degradation behavior. The I
D–V
G characteristic exhibits a clear negative shift under mechanical strain regardless of the tension or compression state. In addition, the C–V characteristic curves show a leftward shift with extra distortion or stretching out under mechanical strain. This indicates that InGaZnO generates additional defects under this mechanical strain, a phenomenon that can be attributed to the generation of mechanical-strain-induced oxygen vacancies on the flexible a-InGaZnO TFTs.
Polycrystalline thin-films of Zn 1Àx Mg x O (0 x 0:36) have been prepared by a sol-gel method and a spin-coating technique. In this work, the authors investigate the effects of the Mg addition on crystallization, microstructure and optical properties for ZnO thin films. Mg was incorporated into ZnO thin films that were deposited onto glass substrates by a spin coating technique. The as-deposited films were preheated at 300 C for 10 min and then annealed at 500 C for 1 h. The results show that addition of Mg-species in ZnO films markedly decreased surface roughness, improved transparency in the visible range and increased resistivity. Among the Zn 1Àx Mg x O films investigated in the present study, the Zn 0:8 Mg 0:2 O thin film exhibited the best properties, namely single wurzite phase, an optical transmittance of 94.7%, an RMS roughness of 1.63 nm and a resistivity of 8:3 Â 10 5 -cm.
This paper investigates the degradation behavior of InGaZnO thin film transistors (TFTs) under negative bias illumination stress (NBIS). TFT devices with two different source and drain layouts were exanimated: one having a parallel format electrode and the other with UI format electrode. UI means that source/drain electrodes shapes is defined as a forked-shaped structure. The I-V curve of the parallel electrode exhibited a symmetric degradation under forward and reverse sweeping in the saturation region after 1000 s NBIS. In contrast, the I-V curve of the UI electrode structure under similar conditions was asymmetric. The UI electrode structure also shows a stretch-out phenomenon in its C-V measurement. Finally, this work utilizes the ISE-Technology Computer Aided Design (ISE-TCAD) system simulations, which simulate the electron field and IV curves, to analyze the mechanisms dominating the parallel and UI device degradation behaviors.
This letter investigates repeated uniaxial mechanical stress-induced degradation behavior in flexible amorphous In-Ga-Zn-O thin-film transistors (TFTs) of different geometric structures. Two types of via-contact structure TFTs are investigated: symmetrical and UI structure (TFTs with I- and U-shaped asymmetric electrodes). After repeated mechanical stress, I-V curves for the symmetrical structure show a significant negative threshold voltage (VT) shift, due to mechanical stress-induced oxygen vacancy generation. However, degradation in the UI structure TFTs after stress is a negative VT shift along with the parasitic transistor characteristic in the forward-operation mode, with this hump not evident in the reverse-operation mode. This asymmetrical degradation is clarified by the mechanical strain simulation of the UI TFTs.
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