Tunable Threshold Voltage of ZnTe-Based Ovonic Switching Devices via Isovalent Cation Exchange

The neuromorphic system is one of the promising architectures for the next generation of electronic devices. In this system, the selector is pivotal in overcoming the unwanted sneak current issue due to a crossbar array structure in the neuromorphic system and ovonic threshold switches (OTS) are considered as one of the candidates for the selector. A key property of selector materials is the threshold voltage and thus its tunability is significant in terms of the flexibility and selectivity of various devices under different operating conditions. To investigate the tunability of OTS selector materials, in our work, ZnTe-based ternary chalcogenides are chosen as a prototypical example. Based on first-principles calculations, systematic studies into the impact of isovalent cation exchange with alkaline earth metals (Be, Mg, and Ca) have been performed. The thermodynamic stability of considered ternary chalcogenides is studied for different temperatures via a supercell approach. Also, the effects of cation exchange on the electronic structure are thoroughly discussed. In addition, we provide an empirical model to predict possible tunable ranges of the threshold voltage by isovalent cation exchanges for appropriate OTS selector materials.