Abstract
Nowadays thin-film-transistor (TFT) has been widely used in flat panel displays, which is used whether in mobile phone, MP3 or LCD-TV. As the evolution with technology, flat panel display becomes larger and more sophisticated. In the development of large scale display, we need to consider the uniformity of TFT materials. In high-frequency operation (ex. 3-D screen), we have to use the material with higher mobility.The most commonly used materials in TFT are poly-silicon and amorphous-silicon. Compared the poly-Si and a-Si with a-IGZO, the a-IGZO is considered to be the next generation of materials used in TFTs, due to the perfect uniformity and well mobility at same time. However a-IGZO TFT has several instabilities such as gate bias stress, lightillumination and oxygen adsorption effect.Previous studies have discussed the phenomenon. However, the instabilities compared in different ambience are rarely mentioned. Now we investigate on the environment-dependent bias stress and photosensitive characteristics of a-IGZO TFT. We use Positive/Negative Bias Stress (PBS/NBS) and light-illumination in different ambience to discuss the degradation of a-IGZO TFT. We found the positive bias stress (PBS) induce the oxygen adsorption on a-IGZO surface by the increasing electron concentration. Besides, the negative bias stress didn’t not cause any degradation on a-IGZO in any kind of environment by channel carrier depletion. Although oxygen will cause the higher threshold voltage, oxygen can effectively suppress the negative threshold voltage shift causedby photo-generated charges.