Atomic layer-deposited Ta2O5−x nano-islands for charge trapping memory devices

Abstract

Charge trapping memory (CTM) boasts numerous advantages over conventional flash memory, making it a suitable alternative. In this work, atomic layer-deposited Ta₂O_5−x nano-islands were employed as charge trapping units in a Pt/Al₂O₃/Ta₂O_5−x nano-island/Al₂O₃/Si structure for data storage. The effect of the dimension and areal density of Ta₂O_5−x nano-islands on memory characteristics was investigated by tuning growth cycles. It was found that the surface of Al₂O₃ as a tunneling layer has the most abundant active groups (–OH), which facilitate the nucleation and growth of Ta₂O_5−x. The measured areal density of Ta₂O_5−x nano-islands was 6.30 × 10¹¹ cm⁻² after 20 cycles with an average width and height of 10.8 and 1.4 nm, respectively. The memory cell with 20-cycle Ta₂O_5−x nano-islands exhibits optimal charge storage capability with a memory window of 5.8 V and charge storage density of 1.11 × 10¹³ cm⁻² at ±12 V sweeping voltage, which is superior to the control sample with a 50-cycle continuous Ta₂O_5−x thin film. The cell also manifests fast program/erase speed, excellent endurance properties and acceptable retention characteristics. Moreover, the Ta₂O_5−x nano-island CTM device shows promising potential as an optoelectronic synaptic device or photodetector.