The effect of Al₂O₃ passivation layer in pulsed-laser-deposited ZrO₂ films on n-GaAs substrate as a function of post-annealing temperature

We investigated the thermal stability of ZrO₂/GaAs structures deposited by pulsed laser deposition as a function of the post-annealing temperature. During the annealing process the interfacial layer between the pulsed laser deposited ZrO₂ thin film and GaAs substrate increased significantly at the temperature of 500°C, and the ZrO₂ thin film became fully crystallized to the monoclinic phase at the temperature of 600°C. This resulted in the degradation of electrical properties such as the leakage current and the breakdown voltage, and an interfacial trap charge density. In order to improve the thermal stability, we pre-deposited an Al ₂O₃ passivation layer by atomic layer deposition followed by pulsed laser deposited ZrO₂ deposition. The amorphous Al ₂O₃ passivation layer hindered the crystallization of the ZrO₂ thin film during the annealing process, significantly improving the electrical characteristics of the resulting structure compared to the ZrO₂/GaAs structures without an Al₂O₃ passivation layer. In particular, the interfacial reaction was effectively suppressed up to a temperature of 600°C so that the interface trap charge density was significantly decreased due to the low oxygen diffusivity of Al ₂O₃ layer.