ALD Heterojunction Ovonic Threshold Switches

Conformal atomic layer deposition (ALD) of chalcogenide films would enable aggressive 3D integration of nonvolatile memories; unfortunately, the fabrication of high-performance ALD OTSs remains an unsolved problem. Here we present an ALD process to incorporate As in a quaternary GeAsSeTe (GAST) film showing excellent conformality, controllable thickness, and composition homogeneity. The films were used to produce a GeSe/GAST heterojunction-OTS selector. We demonstrate low leakage current (∼10–9 A over a 0.01 μm2 area measured at VTH/2), a VTH ∼ 3 V, a switching time of ∼2 ns—and an outstanding endurance exceeding 109 cycles—on par with the current OTS state-of-the-art.