Investigation of lithium (Li) doping on the resistive switching property of p-Li:NiO/n- β -Ga2O3thin-film based heterojunction devices

Abstract

Li-doped NiO/ β-Ga2O3 polycrystalline bilayer thin-film pn-heterojunctions with different Li-doping concentrations are grown on Si-substrates using the pulsed laser deposition technique. Resistive switching property of these devices has been investigated in detail. This study shows that the Li-doping concentration in NiO layer significantly influences the performance of these devices. For an optimum Li-doping of 1.5%, a stable memory window of ∼102 with endurance of more than 100 cycles and long retention time can be achieved. The coefficient of variation (C v) of SET and RESET voltages also found to ∼20% and ∼40%, respectively, satisfying the acceptability benchmark. A transition from complementary resistive switching (CRS) to bipolar resistive switching (BRS) after multiple sweeping operations has been observed in devices with intermediate Li-doping concentrations. Observation of CRS has been explained in terms of the formation of Li-rich metallic layer at the NiO/Ga2O3 interface as a result of out-diffusion of Li. Redistribution of the Li-ions from the Li-rich interfacial zone to whole of the NiO layer after first few sweeping cycles must be the reason for CRS-to-BRS transition. Results further suggest that return to high resistive state via Poole-Frenkel (PF) pathway during the RESET process might be the key to achieve high performance in p-n junction based resistive switching devices. This study, thus, presents Li-doping as a possible route to modulate the resistive switching property of bilayer Li:NiO/Ga2O3 based memory devices.