Effects of gate roughness on low voltage InGaZnO thin-film transistors with ultra-thin anodized AlxOy dielectrics

Low-voltage oxide semiconductors thin-film transistors (TFTs) with ultra-thin dielectrics are gaining attention in wearable electronics. However, it is a challenge for oxide semiconductor TFTs to operate at a low-voltage while maintaining high performance. In this article, ultra-thin AlxOy films (∼3 nm) are grown on aluminum (Al) electrodes with different surface roughness by anodization. The morphology and electrical properties of the anodized AlxOy films are studied. Furthermore, InGaZnO (IGZO) TFTs with the anodized AlxOy dielectrics are fabricated. It is revealed that the rougher Al gate electrode deposition resulted in a higher interface trap density, which lead to the degradation of device performance. Through optimizing the surface roughness of the initial Al gate electrodes that are used for anodization, the IGZO TFTs can operate at 1 V and show desirable properties including a reasonable saturation mobility of 5.5 cm2 V−1s−1, a low threshold voltage of 0.37 V, a small subthreshold swing of 79 mV decade−1, and a high current on-off ratio of over 106. This work shows the potential of using anodization in the future for low-power wearable electronics.