Novel Zn-Doped ${\rm Al}_{2}{\rm O}_{3}$ Charge Storage Medium for Light-Erasable In–Ga–Zn–O TFT Memory

A novel Zn-doped Al₂O₃ (ZAO) layer prepared by atomic layer deposition (ALD) is used as the charge storage medium in an In-Ga-Zn-O thin-film-transistor memory. The gate insulating stack of Al₂O₃/ZAO/Al₂O₃ is assembled in a single ALD step, and is found to possess a high electron storage capacity due to very deep defect levels. The memory device shows a threshold voltage shift as large as 6.38 V after a +15V/1 ms programming pulse, and quite good charge retention. Once programmed, the memory can be only light erased. The underlying mechanisms are discussed with the assistance of density functional theory calculations.