Artificial semiconductor/insulator superlattice channel structure for high-performance oxide thin-film transistors

High-performance thin-film transistors (TFTs) are the fundamental building blocks in realizing the potential applications of the next-generation displays. Atomically controlled superlattice structures are expected to induce advanced electric and optical performance due to two-dimensional electron gas system, resulting in high-electron mobility transistors. Here, we have utilized a semiconductor/insulator superlattice channel structure comprising of ZnO/Al ₂O₃ layers to realize high-performance TFTs. The TFT with ZnO (5 nm)/Al₂O₃ (3.6 nm) superlattice channel structure exhibited high field effect mobility of 27.8 cm² /Vs, and threshold voltage shift of only < 0.5 V under positive/negative gate bias stress test during 2 hours. These properties showed extremely improved TFT performance, compared to ZnO TFTs. The enhanced field effect mobility and stability obtained for the superlattice TFT devices were explained on the basis of layer-by-layer growth mode, improved crystalline nature of the channel layers, and passivation effect of Al₂O₃ layers.