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Ferroelectric‐Like Charge Trapping Thin‐Film Transistors and Their Evaluation as Memories and Synaptic Devices
Author(s) -
Daus Alwin,
Lenarczyk Pawel,
Petti Luisa,
Münzenrieder Niko,
Knobelspies Stefan,
Cantarella Giuseppe,
Vogt Christian,
Salvatore Giovanni A.,
Luisier Mathieu,
Tröster Gerhard
Publication year - 2017
Publication title -
advanced electronic materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.25
H-Index - 56
ISSN - 2199-160X
DOI - 10.1002/aelm.201700309
Subject(s) - materials science , optoelectronics , thin film transistor , neuromorphic engineering , dielectric , transistor , trapping , ferroelectricity , amorphous solid , thin film , voltage , nanotechnology , electrical engineering , layer (electronics) , computer science , ecology , chemistry , engineering , organic chemistry , machine learning , artificial neural network , biology
This work presents a defect charging mechanism in 5‐nm‐thick amorphous Al 2 O 3 thin‐films fabricated on plastic, which leads to multistate memory effects, and thus the realization of synaptic thin‐film transistors (TFTs) for neuromorphic applications. First, the Al 2 O 3 thin‐films are characterized in metal–insulator–metal stacks. These devices exhibit ferroelectric‐like behavior, which is visible in the small‐signal capacitance and the surface charge density. Furthermore, the quantum‐mechanical simulation of the current–voltage characteristic leads to a physical model with trap charges close to the anode interface where deep‐level traps are identified by fitting the experimentally obtained resonant tunneling peaks. The trap charge lifetime and frequency behavior is evaluated in InGaZnO 4 TFTs, where the 5‐nm‐thick Al 2 O 3 layer is employed as gate dielectric. At an operating voltage as low as ±2 V, a charge trapping retention up to ≈3 h and a discernable ON/OFF read‐out with a factor >3 at 2 kHz are achieved. When subjected to a train of gate–source voltage pulses, the TFTs show charge integration properties which emulate facilitating and depressing behaviors of biological synapses. These results indicate that thin low‐temperature defect‐rich metal‐oxide dielectrics may be candidates for low‐voltage memory applications and neuromorphic circuits on unconventional substrates.