Chinese scholars have made new progress in thermal/electrical integration rectification

Fig.
1 Preparation and characterization of MoSe 2-WSe₂ heterojunction rectifier devices at different interface angles

Fig.
2 Measurement results of electrical and thermal rectification characteristics of MoSe 2-WSe₂ heterojunction devices

With the support of the National Natural Science Foundation of China (grant numbers: 51976096, 51827807, 52130602), Professor Zhang Xing, Associate Professor Wang Haidong of the School of Aeronautics and Astronautics of Tsinghua University and Associate Professor Lv Ruitao of the School of Materials successfully developed the first two-dimensional in-plane heterojunction thermal/electrical integrated rectifier, which obtained an electrical rectification ratio of up to 10⁴ and a thermal rectification ratio
of 96% at the two-dimensional heterojunction interface of atomic thickness 。 The study, titled "Simultaneous electrical and thermal rectification in a monolayer lateral heterojunction," was recently published in
the journal Science.
Links to papers: _istranslated="1">.

Chip is the "stuck neck" problem of China's core technology, and with the gradual reduction of chip size, new challenges
have been posed to the fields of material science and thermal science.
On the one hand, the gate width of traditional silicon-based transistors has reached its physical limit, and it is necessary to find the next generation of new semiconductor materials to further improve the integration of
chips 。 Single-layer transition metal dichalcogenides (TMDCs) are expected to replace silicon-based materials to further reduce the transistor size due to their atomic thickness and extremely high switching ratio.
On the other hand, the high integration of chips will lead to a significant increase in local heat flux density, and heat dissipation has become a key problem hindering the development of the chip industry, but due to the ubiquitous three-phonon scattering in semiconductor materials, the thermal conductivity of the material decreases with the increase of temperature, which will accelerate the thermal failure
of the chip under high-power working conditions.

In order to solve the above problems, the research team used the Atmospheric-Pressure Chemical Vapor Deposition (AP-CVD) method to synthesize a monolayer MoSe 2-WSe_2-in-plane heterojunction material.
High-precision nanopositioning and electron beam exposure processing techniques were used to prepare suspension H-type electronic devices with different interface angles (Figure 1).

Measurements show that the device has an electrical rectification ratio of up to 10⁴ and a thermal rectification ratio of 96% when electrons and phonons pass perpendicular through the heterojunction interface (Figure 2).

The research team further found that the thermal rectification effect will significantly improve the heat dissipation ability of electronic devices under high-power conditions, when the diode device is in the forward conduction state, the current through the device increases rapidly with the increase of power, forming a significant temperature gradient from MoSe 2 to_{WSe 2}, so that the thermal conductivity in this direction increases by 96%.

。 The increase in the thermal conductivity of the material will significantly improve the heat dissipation performance of the device, and the experimental measurement results show that the single-layer 2D heterojunction rectifier device can withstand a large bias voltage of 60 V, and the local hot spot temperature rise of the device is reduced by about 20%
compared with the no thermal rectification condition.

The study shows that the new two-dimensional in-plane heterojunction device not only has the advantages of atomic thickness, wide bandgap and high mobility, but also significantly improves the thermal conductivity of the material in a specific direction under high-power working conditions, which can greatly reduce the temperature and thermal stress of high temperature hot spots without external cooling, effectively improving device performance and prolonging service life
.
The research results are expected to change the traditional idea of relying only on external means to cool chips, and fundamentally solve the heat dissipation problem
of high-power chips by improving the thermal conductivity of semiconductor materials themselves.