Nature Electronics | Volume 7 | March 2024 | 216–224
216
nature electronics
Article https://doi.org/10.1038/s41928-024-01129-9
Two-dimensional perovskite oxide as a
photoactive high-κ gate dielectric
Siyuan Li
1,2
, Xinya Liu
1,2
, Hui Yang
1
, Hong Zhu
1
& Xiaosheng Fang
1
High dielectric constant (high-κ) gate dielectrics compatible with
two-dimensional (2D) semiconductors are essential for scaled optoelectronic
devices. However, conventional three-dimensional dielectrics are dicult
to integrate with 2D materials with dangling-bond-free surfaces. Here
we show that the 2D perovskite oxide Sr
2
Nb
3
O
10
, prepared by a top-down
approach, can be integrated with various 2D channel materials. The high
dielectric constant (24.6) and moderate bandgap of Sr
2
Nb
3
O
10
allow it
to be used as a photoactive high-κ dielectric for phototransistors with
various 2D channel materials, including graphene, molybdenum disulde,
tungsten disulde and tungsten diselenide. Molybdenum disulde
transistors exhibit an on/o ratio of 10
6
with a supply voltage of 2 V and a
subthreshold swing of 88 mV dec
−1
. Tungsten disulde phototransistors
exhibit a photocurrent-to-dark-current ratio of ~10
6
and ultraviolet (UV)
responsivity of 5.5 × 10
3
A W
−1
under visible or UV light illumination, due to
the combined eect of gate control and charge transfer from the photoactive
gate dielectric. We also show that the phototransistors with the photoactive
dielectric can oer UV–visible dual-band photodetection, where UV and
visible light illumination are distinguished at separate terminals.
Two-dimensional (2D) semiconductors are promising channel materials
for scaling optoelectronic devices
1–3
. Miniaturized devices require higher
gate capacitance to improve device performance and reduce power
consumption. One method to improve gate capacitance without greatly
reducing the physical thickness of gate dielectrics—which is essential for
efficient gate control and low leakage current
4–6
—is to use high dielectric
constant (high-κ) gate dielectrics such as hafnium oxide (HfO
2
). However,
their integration with 2D semiconductors remains challenging.
For conventional deposition methods, the non-uniform
nucleation of amorphous dielectrics (such as Al
2
O
3
and HfO
2
) on
dangling-bond-free 2D semiconductors degrades the interface qual-
ity
5,7
. High-energy deposition processes can also damage the surface of
2D materials and thus deteriorate device performance
8,9
. Other high-κ
candidates include native oxides (such as HfSe
2
/HfO
2
and Bi
2
O
2
Se/
Bi
2
SeO
5
) and epitaxially grown dielectrics (such as CaF
2
on Si(111) sur-
face), but these are limited by the scarcity of native oxides and harsh
growth conditions
10–13
. Transferring as-prepared high-κ dielectrics
onto 2D materials has demonstrated its potential for damage-free
integration, circumventing the issues of lattice matching and process-
ing compatibility
14–18
. However, most reports on transfer integration
involve high-κ dielectrics with three-dimensional structures
14,16,19
, which
makes it challenging to synthesize them with reduced thickness and
well-defined surfaces.
The bandgap of dielectrics is important in achieving a favourable
band offset with the target channel material and for their optoelec
-
tronic properties
20,21
. The bandgap of dielectric candidates is inversely
correlated with the dielectric constant
21,22
. For example, dielectrics with
wide bandgaps, such as silicon dioxide (SiO
2
) and hexagonal boron
nitride (hBN), are transparent to light and have relatively low dielectric
constants. In contrast, dielectrics with high dielectric constant (such
as titanium oxide) suffer from large leakage currents due to the low
bandgap and unfavourable band offset
22
. Therefore, a balance between
the dielectric constant and bandgap should be achieved when multiple
functionalities are integrated in a single miniaturized device platform.
Received: 7 December 2022
Accepted: 1 February 2024
Published online: 1 March 2024
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1
Department of Materials Science, State Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai, P. R. China.
2
These authors contributed equally: Siyuan Li, Xinya Liu. e-mail: xshfang@fudan.edu.cn