Anomalous Current–Voltage Behavior in Al/TiO2/n‐Si Structures

The current–voltage (J–V) curves of Al/TiO2/n‐Si structures present an anomalous behavior where the current becomes constant for a reverse bias higher than ≈0.65 V. Here we analyze devices fabricated by spin‐coating of an organometallic precursor and subsequent annealing in an O2 atmosphere. The details of the current saturation phenomenon are interpreted as a consequence of the formation of a depletion region in Si, which limits the voltage drop in the film and truncates the current. The analysis is supported experimentally by capacitance–voltage and photoconductance measurements. It is also shown that the saturation current can be controlled by modifying the film's deposition conditions, changing the barrier for electron injection from Al to TiO2. The current through Al/TiO2/n‐Si structures becomes constant when a voltage higher than about 0.65 V is applied in Si with respect to Al, even though the band's energy alignment should allow easy electron injection in TiO2 from both sides. In this paper Razera et al. explain this anomaly. It is due to the formation of a depletion region in Si that compensates the negative charges accumulated in TiO2 because of the space‐charge‐limited‐current mechanism.