Zn vacancy complex-determined filamentary resistive switching characteristics in Au/ZnSe/ITO chalcogenide-based memory cells

Abstract

ZnSe films with a sphalerite structure and about 100nm grain size were deposited on ITO substrate. 200 stable bipolar resistive switching (RS) cycles were obtained in Au/ZnSe/ITO chalcogenide-based memory cells and it shows an ON/OFF ratio of 10 and retention time of 104 seconds. The conduction mechanism is Ohmic in both low resistance state (LRS) and low voltage region in high resistance state (HRS) while thermionic emission limited conduction (TELC) at high voltage region in HRS. The top electrode (TE) size independence of low resistance implies a filamentary resistive switching mechanism. Photoluminescence (PL) spectroscopy shows a double difference of relative intensity between shallow zinc vacancy state and deep zinc vacancy complex state in HRS and LRS. The explanation for HRS is the dissociation of zinc vacancy complex and the formation of zinc vacancy. Then the shallow acceptor zinc vacancy compensates for the shallow donor contributing the HRS. It is deduced from linear relation of reset voltage and reset power versus temperature that the thermal activation energy of ZnSe film is 0.19 eV, which indicates an over 20nm intertrap distance and the critical temperature for conductive filament (CF) rupture is 305.6K with 0.2mV/s sweep rate, respectively. The component of CF is metal-like shallow donor such as Al or Ga with the help of deep zinc vacancy complex to depress the compensation of shallow zinc vacancy acceptor.