High-performance CdScInO thin-film transistors and their stability improvement under negative bias (illumination) temperature stress

Abstract

Recently, the performance of thin-film transistors (TFTs) with amorphous oxide semiconductors (AOSs) has been substantially improved. However, the device reliability under negative bias illumination/temperature stress (NBI/TS) remains a critical issue. Herein, a Cd and Sc co-doped In₂O₃ semiconductor (CdScInO) is developed for improving the NBI/TS stability of TFTs. The mobility, subthreshold swing, and on/off ratio of the CdScInO TFT are 15.9 cm² V⁻¹ s⁻¹, 89 mV dec⁻¹ and ∼10⁷, respectively. More interestingly, the CdScInO TFTs exhibit excellent stability under NBTS at 80 °C or under NBIS with red light or green light illumination, while a threshold voltage shift of only −0.91 V is observed under NBIS with blue light illumination for 3600 s. First-principles calculations show that the Cd dopants cause the formation of holes, which can be bound with oxygen vacancies (V_Os) to form Cd–V_O pairs. Furthermore, the density of states near the valence band maximum decreases due to the upward repulsion between the O p states and the Cd d states. Thus, the activation of V_O or electron donor defects is suppressed, which explains the NBI/TS stability improvement for CdScInO TFTs.