Electric Field Gradient‐Controlled Domain Switching for Size Effect‐Resistant Multilevel Operations in HfO₂‐Based Ferroelectric Field‐Effect Transistor

Abstract

The ferroelectric field-effect transistor (FeFET) is a promising memory technology due to its high switching speed, low power consumption, and high capacity. Since the recent discovery of ferroelectricity in Si-doped HfO 2 thin films, HfO 2 -based materials have received considerable interest for the development of FeFET, particularly considering their excellent complementary metal-oxide-semiconductor (CMOS) compatibility, relatively low permittivity, and high coercive field. However, the multilevel capability is limited by the device size, and multidomain switching tends to vanish when the channel length of the HfO 2 -based FeFET approaches 30 nm. Here, multiple nonvolatile memory states are realized by tuning the electric field gradient across the Hf 0.5 Zr 0.5 O 2 (HZO) ferroelectric thin film along the channel direction of FeFET. The multi-step domain switching can be readily and directionally controlled in the HZO-FeFETs, with a very low variation. Moreover, multiple nonvolatile memory states or multi-step domain switching can be effectively controlled in the FeFETs with a channel length less than 20 nm. This study suggests the possibility to implement multilevel memory operations and mimic biological synapse functions in highly scaled HfO 2 -based FeFETs.

High‐Performing Self‐Powered Photosensing and Reconfigurable Pyro‐photoelectric Memory with Ferroelectric Hafnium Oxide

“…[ 10,11 ] Besides the orthorhombic phase, the monoclinic phase is also observed, which is known to be the most common phase at room temperature and ambient pressure (see Figure 1c). [ 4,10,31,32 ] Further, the average interplanar spacing (≈0.29 nm) matches closely to the (111) plane of the monoclinic HfO 2 phase (see line profile in the inset of Figure 1c). The monoclinic phase is the stable form, and therefore, when the amorphous film transforms into it, the phase transition is complete.…”

“…The typical hysteresis loop appeared in the P – V measurements and loop opening improved with increasing the scanning voltage range; for instance, the loop opening (i.e., 2 P ) was 2.52 µC cm −2 for scan voltages of 0 → +1.0 → 0 → −1.0 → 0 V, whereas it improved to 4.93 µC cm −2 for ±8.0 V scanning. [ 4,10,11 ] Further, the current–voltage ( I – V herewith) collected during the P – V measurements shows two distinct current peaks associated with polarization switching (see Figure S3, Supporting Information). Indeed, the appearance of clear loop openings in P – V and corresponding peaks in the I – V measurements indicate the ferroelectric behavior of the device.…”

“…[ 1–3 ] In this scenario, recently, one of the most emerging materials is hafnium oxide (HfO 2 ), which maintains ferroelectricity even below a thickness of less than 5 nm, resulting in offering a scaling at sub‐nanometer for complementary metal–oxide–semiconductor (CMOS) compatible electronic/optoelectronic microelectronics technology; indeed, beyond Moore's era. [ 4,5 ] Generally, an electric pulse is used to store information in two‐terminal ferroelectric‐based memory devices, which are read‐out by a sequential, however, destructive electric pulse. [ 6,7 ] Therefore, the data requires rewriting after each reading operation, which is not favorable for energy‐efficient applications like memory storage, object recognition, and trainable object classification.…”

Photo‐Synaptic Oxide Transistors with Al2O3/SiOx Stacked Gate Dielectric Exhibiting 1024 Conduction States with Good Linearity

“…This number of states is significantly higher compared to previously reported synaptic devices using voltage and light stimuli. [ 9,13,14,19 ] In particular, the number of conduction states, 1024, is considerably higher than those previously reported for TiO 2 ‐based transistors that employ only Al 2 O 3 dielectrics. [ 15 ] These results are obtained primarily owing to the presence of the CID in the proposed device.…”

A Multifunctional Flexible Ferroelectric Transistor Sensor Based on Si/Fe‐Doped Indium Oxide for Electronic Skin

“…Polymers based on ferroelectric polymers have been extensively explored in nonvolatile memory and mechanical sensing applications, as well as energy harvesting [27]. To alter the conductivity of the semiconductor layer, ferroelectric polymers may be combined with ferroelectric field-effect transistors (FeFETs), which modify the threshold voltage of the FeFET device in response to changes in the polarization state of the ferroelectric layer [28][29][30]. Mechanical and thermal stimuli will affect the polarization state and threshold voltage of the FeFETs, which is predicted to be sensitive to both piezoelectric and thermoelectric capabilities.…”