Highly Uniform Resistive Switching Performances Using Two-Dimensional Electron Gas at a Thin-Film Heterostructure for Conductive Bridge Random Access Memory

This research demonstrates, for the first time, the development of highly uniform resistive switching devices with self-compliance current for conductive bridge random access memory using two-dimensional electron gas (2DEG) at the interface of an Al₂O₃/TiO₂ thin-film heterostructure via atomic layer deposition (ALD). The cell is composed of Cu/Ti/Al₂O₃/TiO₂, where Cu/Ti and Al₂O₃ overlayers are used as the active/buffer metals and solid electrolyte, respectively, and the 2DEG at the interface of Al₂O₃/TiO₂ heterostructure, grown by the ALD process, is adopted as a bottom electrode. The Cu/Ti/Al₂O₃/TiO₂ device shows reliable resistive switching characteristics with excellent uniformity under a repetitive voltage sweep (direct current sweep). Furthermore, it exhibits a cycle endurance over 10⁷ cycles under short pulse switching. Remarkably, a reliable operation of multilevel data writing is realized up to 10⁷ cycles. The data retention time is longer than 10⁶ s at 85 °C. The uniform resistance switching characteristics are achieved via the formation of small (∼a few nm width) Cu filament with a short tunnel gap (<0.5 nm) owing to the 2DEG at the Al₂O₃/TiO₂ interface. The performance and operation scheme of this device may be appropriate in neuromorphic applications.