Li-Well ZnO Memtransistors: High Reliability for Neuromorphic Applications

Abstract

Memtransistors are active analog memory devices utilizing ionic memristive materials as channel layers. Since their introduction, the term “memtransistor” has widely been adopted for transistors exhibiting nonvolatile memory characteristics. Currently, memtransistor devices possessing both transistor on/off functionality and nonvolatile memory characteristics include ferroelectric field-effect transistors (FeFETs) and charge-trap flash (floating gate), yet ionic memtransistors have not matched their performance. Here a facile and extendable lithium (Li)-well oxide memtransistor (LWOM) is reported as a promising candidate. Forming a Li well, analogous to an n+ well beneath electrodes in n-metal-oxide-semiconductor field-effect transistor (MOSFET) processes, induces Li⁺-ion migration via write VDS, achieving analog memory characteristics through Schottky barrier modulation. LWOM enables low-voltage weight updates and precise gate-controlled weight update characteristics. Analysis via 3D secondary ion mass spectrometry (SIMS) confirms Li-ion redistribution and the resistance-switching mechanism. A 21 × 21 crossbar array demonstrates 99.31% operational yield and successful weight updates to target conductance values. Fabricated using mature oxide semiconductor technology with a 230 °C thermal budget and a simple process, LWOM stands as a strong contender for next-generation nonvolatile memory and artificial neural network (ANN) acceleration hardware.