4.0-inch Active-Matrix Organic Light-Emitting Diode Display Integrated with Driver Circuits Using Amorphous In–Ga–Zn-Oxide Thin-Film Transistors with Suppressed Variation

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We have newly developed a 4.0-in. quarter video graphics array (QVGA) active-matrix organic light-emitting diode (AMOLED) display integrated with gate and source driver circuits using amorphous In–Ga–Zn-oxide (IGZO) thin-film transistors (TFTs). Focusing on a passivation layer in an inverted staggered bottom gate structure, the threshold voltage of the TFTs can be controlled to have “normally-off” characteristics with suppressed variation by using a SiOx layer formed by sputtering with a low hydrogen content. In addition, small subthreshold swing $S/S$ of 0.19 V/decade, high field-effect mobility $\mu_{\text{FE}}$ of 11.5 cm2 V-1 s-1, and threshold voltage $V_{\text{th}}$ of 1.27 V are achieved. The deposition conditions of the passivation layer and other processes are optimized, and variation in TFT characteristics is suppressed, whereby high-speed operation in gate and source driver circuits can be achieved. Using these driver circuits, the 4.0-in. QVGA AMOLED display integrated with driver circuits can be realized.
2010-03-25