Power Dissipation of WSe₂ Field-Effect Transistors Probed by Low-Frequency Raman Thermometry

Abstract

The ongoing shrinkage in the size of two-dimensional (2D) electronic circuitry results in high power densities during device operation, which could cause a significant temperature rise within 2D channels. One challenge in Raman thermometry of 2D materials is that the commonly used high-frequency modes do not precisely represent the temperature rise in some 2D materials because of peak broadening and intensity weakening at elevated temperatures. In this work, we show that a low-frequency E shear mode can be used to accurately extract temperature and measure thermal boundary conductance (TBC) in back-gated tungsten diselenide (WSe) field-effect transistors, whereas the high-frequency peaks (E and A) fail to provide reliable thermal information. Our calculations indicate that the broadening of high-frequency Raman-active modes is primarily driven by anharmonic decay into pairs of longitudinal acoustic phonons, resulting in a weak coupling with out-of-plane flexural acoustic phonons that are responsible for the heat transfer to the substrate. We found that the TBC at the interface of WSe and Si/SiO substrate is ∼16 MW/m K, depends on the number of WSe layers, and peaks for 3-4 layer stacks. Furthermore, the TBC to the substrate is the highest from the layers closest to it, with each additional layer adding thermal resistance. We conclude that the location where heat dissipated in a multilayer stack is as important to device reliability as the total TBC.

A Review of Experimental and Computational Advances in Thermal Boundary Conductance and Nanoscale Thermal Transport across Solid Interfaces

“…It was also shown that increasing the number of boron nitride layers (to a total thickness of 12.8 nm) led to a reduction of as much as ≈50% in the measured h K . Tungsten diselenide on SiO 2 substrate showed similar thickness dependent behavior as reported by Behranginia et al via an electronic‐heating Raman‐probe platform. However, the conductance was shown to peak for 3 to 4 layers of WSe 2 with a value of 32 MW m −2 K −1 .…”

High‐Electric‐Field‐Induced Phase Transition and Electrical Breakdown of MoTe2

“…As high performance and low power devices are more in need to meet the harsh requirements of the emerging mobile and Internet of Things (IoT) environment, it becomes clear that energy dissipation and electrical breakdown are formidable challenges, toward the realization of further miniaturization and functionalized integration of 2D electronics 7–12. Power dissipation in 2D materials, including graphene, black phosphorus, and other TMDCs, has been studied by Raman spectroscopy under the high electrical fields applied to the FET structure 11,13–16. To the best of our knowledge, the power dissipation and electrical breakdown of molybdenum ditelluride (MoTe 2 ) have not been studied intensively, although it is one of the most promising TMDCs that can be employed for future 2D device applications requiring ambipolar semiconducting properties 17–20.…”

“…The simultaneous measurement of electrical currents and Raman shifts on 2D materials enables to reveal the temperature profile of 2D materials induced by the Joule heating. It is obviously important to examine the energy dissipation of 2D electronics and the thermal state on their surface under electrical biasing 11,13–16. In this work, we investigated the electrical breakdown and phase transition of MoTe 2 , and examined the effects of voltage and temperature on Raman shifts from various thickness MoTe 2 transistors.…”

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including graphene, black phosphorus, and other TMDCs, has been studied by Raman spectroscopy under the high electrical fields applied to the FET structure. [11,[13][14][15][16] To the best of our knowledge, the power dissipation and electrical breakdown of molybdenum ditelluride (MoTe 2 ) have not been studied intensively, although it is one of the most promising TMDCs that can be employed for future 2D device applications requiring ambipolar semiconducting properties. [17][18][19][20] MoTe 2 is known to have a 2H semiconducting phase with the thickness dependent band gap in the range from 0.83 to 1.1 eV.

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“…It is obviously important to examine the energy dissipation of 2D electronics and the thermal state on their surface under electrical biasing. [11,[13][14][15][16] In this work, we investigated the electrical breakdown and phase transition of MoTe 2 , and examined the effects of voltage and temperature on Raman shifts from various thickness MoTe 2 transistors. Interestingly, MoTe 2 seems to show an unusual electrical breakdown, perhaps related to the phase transition.…”