In-gap electronic states of GeAsSe and SiGeAsSe alloys for selector devices from atomistic simulations

GeAsSe alloys are of interest for application in selector devices in combination with both phase change and resistive memories. In this work, we compute the electronic properties of GeAsSe alloys at several compositions and of a Si-doped GeAsSe alloy within Density Functional Theory (DFT). The analysis of the amorphous models generated by quenching from the melt within DFT molecular dynamics aims at gaining information on in-gap states that are believed to control the functional properties of these alloys exploited in the selector devices, namely the switching threshold voltage, its dependence on the preparation conditions of the amorphous material, and its drift with time. The simulations reveal that localized empty in-gap states (electron traps) are mostly related to homopolar Ge[sbnd]Ge, As[sbnd]As and Ge[sbnd]As bonds, while the most localized filled states (hole traps) are mostly related to Se[sbnd]Se bonds and are particularly evident in Se-rich compositions.