Tuning Polarity in WSe₂/AlScN FeFETs via Contact Engineering

Abstract

Recent advancements in ferroelectric field-effect transistors (FeFETs) using two-dimensional (2D) semiconductor channels and ferroelectric Al 0.68 Sc 0.32 N (AlScN) allow highperformance nonvolatile devices with exceptional ON-state currents, large ON/OFF current ratios, and large memory windows (MW). However, previous studies have solely focused on n-type FeFETs, leaving a crucial gap in the development of ptype and ambipolar FeFETs, which are essential for expanding their applicability to a wide range of circuit-level applications.Here, we present a comprehensive demonstration of n-type, ptype, and ambipolar FeFETs on an array scale using AlScN and multilayer/monolayer WSe 2 . The dominant injected carrier type is modulated through contact engineering at the metal−semiconductor junction, resulting in the realization of all three types of FeFETs. The effect of contact engineering on the carrier injection is further investigated through technology-computeraided design simulations. Moreover, our 2D WSe 2 /AlScN FeFETs achieve high electron and hole current densities of ∼20 and ∼10 μA/μm, respectively, with a high ON/OFF ratio surpassing ∼10 7 and a large MW of >6 V (0.14 V/nm).

Complementary memtransistors for neuromorphic computing: How, what and why

“…3(a) [17] . Compar-ing to the current flash memory [23] , it demonstrated several hundred times faster (<10 −6 s), operating voltages four times lower (<5 V), and excellent endurance(>10 8 cycles). Besides, through contact engineering the dominant injected carrier type was modulated at the metal-semiconductor junction, resulting in n-type, p-type and ambipolar FeFET with 2D WSe 2 /Al 0.68 Sc 0.32 N structure [24] .…”

Perspectives of Ferroelectric Wurtzite AlScN: Material Characteristics, Preparation, and Applications in Advanced Memory Devices

“…Empirically, adjusting E c can be effectively achieved by altering the thickness of the thin film. So, we have summarized recent research on the thickness of AlScN films [ 23 , 34 , 36 , 43 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 ], as depicted in Figure 1 c. Such research of thickness reveals a significant downward trend, while the corresponding Sc components gradually concentrate around 0.3. In 2023, it appears to represent a new milestone, with thickness even dropping below 5 nm.…”

“…Just as MOSFETs can be classified into n-channel and p-channel based on their conduction types, FeFETs follow a similar categorization. Kim et al further replaced MoS 2 with 2D material tungsten diselenide (WSe 2 ) as a channel material in 2024 [ 66 ], successfully realizing p-type FeFETs, attributed to the presence of numerous W vacancies in WSe 2 [ 120 ]. Compared to n -type FeFETs, p -type FeFETs exhibit hysteresis loops in the opposite direction.…”

“…Copyright 2021, AIP Publishing. ( c ) Research trends in AlScN film thickness in recent years [ 23 , 34 , 36 , 43 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 ]. ( d ) The cross-sectional TEM image of Al/AlScN/Al and interfaces between layers [ 69 ].…”

Multistate, Ultrathin, Back-End-of-Line-Compatible AlScN Ferroelectric Diodes

“…While many ferroelectric materials have found a wide range of applications in electronic devices, − Al 1– x Sc x N (AlScN) is particularly promising for application in FE diodes due to its distinctive ferroelectric properties. These include a high remnant polarization ( P r ) of >125 μC/cm 2 , a coercive field ( E c ) of 3–6 MV/cm, and a square-shaped polarization – electric field (P – E) loop. , Moreover, Al 1– x Sc x N ( x < 0.43) is highly CMOS BEOL-compatible with a low process temperature (<400 °C) and has a single, stable wurtzite ferroelectric phase, unlike HfO x polymorphisms exhibiting ferroelectricity only in metastable phases .…”