| AVS 60th International Symposium and Exhibition | |
| Electronic Materials and Processing | Wednesday Sessions |
| Session EM+PS-WeM |
| Session: | Oxides and Dielectrics for Novel Devices and Ultra-dense Memory II |
| Presenter: | B. Zhao, University of Washington |
| Authors: | B. Zhao, University of Washington X. Zheng, University of Washington H. Pham, University of Washington M.A. Olmstead, University of Washington F.S. Ohuchi, University of Washington |
| Correspondent: | Click to Email |
Materials exhibiting reversible resistance changes are essential elements of resistance random access memory (R-RAM), which has a simpler structure, lower energy consumption, higher operating speed and higher endurance than conventional RAM. The monoclinic transparent conducting oxide β-Ga2O3 is a promising candidate for R-RAM due to its open-channel structure that enables large scale defect migration. The resistive switching mechanism in pulsed-laser-deposited Ga2O3 was investigated by combining electrical measurements with x-ray diffraction (XRD) and sputter-profiling x-ray photoemission spectroscopy (SP-XPS), revealing a strong correlation of oxide-metal interface conductance with electrically and thermally driven defect migration and agglomeration near the interface.
Electrically-activated reversible resistance switching is observed in thin-film Ni/Ga2O3/Ir, while irreversible changes can be observed upon annealing either single-crystal or thin film gallium oxide. Room-temperature Ni deposition on single crystal β-Ga2O3 results in a rectifying contact with barrier height ~ 0.8 eV and SP-XPS reveals no interface reaction; annealing this structure to 500°C irreversibly creates an ohmic contact, as well as oxidized Ni and reduced Ga at the interface.
A reversible resistance change can be triggered by an electrical pulse in polycrystalline gallium oxide films grown by pulsed laser deposition. Ni/Ga2O3/Ir heterostructures were fabricated and then investigated at different points in their electrical cycling history. Application of less than about 10 V across a 100 nm film (~106 V/cm) maintains the initial Schottky behavior; a 1 sec, 30 V electric pulse switches the metal/oxide contact from Schottky to Ohmic and increases the device conductance by two orders of magnitude. X-ray diffraction shows the film recrystallizes into α and β phases of Ga2O3; further electric field treatment increases the β-phase fraction. Sputter-profiling XPS shows an increase in the near-surface Ga:O ratio and introduction of reduced Ga within 2 nm of the metal-oxide interface. The film remains Ohmic under low voltage cycling, but a high-voltage pulse with the opposite polarity both reverses the interface chemical changes and reverts the electrical characteristic to a Schottky contact. Further cycling between Ohmic and Schottky behavior continues with additional voltage pulses. The results are consistent with Ga interstitial migration and/or an interface redox reaction.
This project is supported by the National Science Foundation under DMR 1104628 and the Micron Foundation.