Impact of radiation induced crystallization on programmable metallization cell electrical characteristics and reliability.

Chalcogenide-based, programmable metallization cells (PMC) cells have been characterized after exposure to increasing levels of absorbed dose (i.e., ionizing radiation exposure). We found, and show here for the first time, that total absorbed dose effects induce a slight modification of the switching phenomena with a moderate increase of the programmable low resistance state (LRS) of the PMCs after repeated switching depending on the processing conditions, while it does not impact the state programmed before exposure. We also show that an increase of the programmable high resistance state (HRS) occurs with irradiation. Such observations are discussed through correlation with crystallization observed in the concurrent X-ray diffraction (XRD) characterization of representative thin-film stacks of the PMCs. These new results are compared to previous results obtained on chalcogenide-based PMCs that did not identify/observe such effects.

Steep-slope field-effect transistors with AlGaN/GaN HEMT and oxide-based threshold switching device.

We report the demonstration of a steep-slope field-effect transistor with AlGaN/GaN MIS-HEMTs employing SiO2-based threshold switching devices in series with the source. The SiO2-based threshold switching devices exhibited steep slope when changing resistance states. The integrated steep-slope transistor showed a low subthreshold swing of sub-5 mV/dec with a transition range of over 105 in the transfer characteristics in both sweep directions at room temperature, as well as the low leakage current (10-5 µA µm-1) and a high I ON/I OFF ratio (>107). Moreover, with the SiO2-based threshold switching devices we also observed a positive shift of threshold voltages of the integrated device. Results from more than 50 transfer characteristics measurements also indicate the good repeatability and practicability of such a steep-switching device, where the average steep slopes are below 10 mV/decade. This steep-slope transistor with oxide-based threshold switching devices can be further extended to various transistor platforms like Si and III-V and are of potential interest for the development of power switching and high frequency devices.

A CMOS-compatible electronic synapse device based on Cu/SiO2/W programmable metallization cells.

In this work, the resistance plasticity of Cu/SiO2/W programmable metallization cell devices is experimentally explored for the emulation of biological synapses. PMC devices were fabricated with foundry friendly materials using standard processes. The resistance can be continuously increased or decreased with both dc and voltage pulse programming. Impedance spectroscopy results indicate that the gradual change of resistance is attributable to the expansion or contraction of a Cu-rich layer within the device. Pulse programming experiments further show that the pulse amplitude plays a more important role in resistance change than pulse width, which is consistent with the proposed 'dual-layer' device model. The dense resistance-state distribution, 1 V operating voltage and inherent CMOS-compatibility suggests its potential application as electronic synapse in neuromorphic computing.