Regimes of leakage current in ALD-processed Al2O3 thin-film layers

A recently known phenomenon of thin oxide layers with thicknesses below approximately 40 nm is the increase in their breakdown electric field, called disruptive strength, towards lower thicknesses. This offers the possibility of examining the current–electric field characteristics at higher electric field strengths without an early electric breakdown. In this paper, we report on the identification of a current regime of trap-free square law and the buildup of an S-shaped current–electric field characteristic curve. This observation for atomic layer deposition (ALD)-processed Al2O3 layers has not been mentioned in the literature so far. Additionally, a modern model of space charge limited current is used to fit the S-shaped characteristic and extract the associated parameters, such as mobility, density of states, and the energy band gap between the conduction band and the trap state. In this context, the Poole–Frenkel effect is neglected in the model to fit our measurements towards the current increase after the trap filled limit. (paper)