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Hafnium indium zinc oxide thin-film transistors (TFTs) with a double-gate structure were evaluated for the first time. Compared with devices with a single bottom gate, TFTs with an additional top gate exhibit improved subthreshold swing, threshold voltage, and field-effect mobility, as well as smaller subthreshold currents upon exposure to visible light. This phenomenon is attributed to the more effective suppression of excess photocurrents by the application of a double-gate structure. Negative-bias stress experiments under illumination indicate that the double-gate TFT exhibits very high stability compared with the device with a single-gate configuration. [ABSTRACT FROM AUTHOR]

We report the electrical stability of double-gate (DG) Ga-In-Zn-O thin-film transistors (TFTs). The threshold voltage (VT) shift of the DG TFT after 3 h of positive-bias temperature stress (VGS = +20 V, VDS = +0.1 V, and Temperature = 60 °C) is as small as +2.7 V, while that of a conventional single-gate (SG) TFT is +6.6 V. The results of negative-bias temperature stress [(NBTS); VGS = -20 V, VDS = +10 V, and Temperature = 60 °C] are more dramatic: The VT shift of the DG TFT is only +0.1 V, whereas that of the SG TFT is -9.1 V. With backlight illumination, the VT shift of the SG TFT under the same NBTS becomes severe (-11.1 V). However, it remains as small as -0.7 V for the DG TFT. [ABSTRACT FROM AUTHOR]

The stability of transparent hafnium-indium-zinc oxide (HIZO) thin-film transistors (TFTs) was investigated under negative-bias stress conditions. TFTs that incorporate transparent electrode materials such as indium-tin oxide or indium-zinc oxide were studied, and the bias stress experiments showed that transparent TFTs undergo severe degradation (negative shift in threshold voltage VT) with simultaneous exposure to white light, in comparison with the results obtained in dark. The time evolution of VT indicates that the deterioration under illumination occurs mainly by the trapping of photogenerated carriers near the HIZO/dielectric interface. [ABSTRACT FROM AUTHOR]

A Ga-In-Zn-O thin-film transistor with double-gate structure is reported. Enhancement-mode operation that is essential to the constitution of a low-power digital circuitry is easily achieved when the upper and lower gate electrodes are tied together. The saturation mobility and the subthreshold swing are improved from 3.65 cm2/(V · s) and 0.44 V/dec to 18.9 cm2/(V · s) and 0.14 V/dec, respectively, compared with the single-gate structure. We can modulate the threshold voltage of either gate by adjusting the bias on the other gate. [ABSTRACT FROM AUTHOR]

The fabrication process and the characteristics of bottom-gate Ga2 03 -In2 03 -ZnO (GIZO) thin-film transistors (TFTs) are reported in detail. Experimental results show that oxygen supply during the deposition of GIZO active layer and silicon oxide passivation layer controls the threshold voltage of the TFT. The field-effect mobility and the threshold voltage of the GIZO TFT fabricated under the optimum process conditions are 2.6 cm2 /V. s and 3.8 V, respectively. A 4-in QVGA active- matrix organic light-emitting diode display driven by the GIZO TFTs without any compensation circuit in the pixel is successfully demonstrated. [ABSTRACT FROM AUTHOR]