Heat Conduction In Semiconductors Research Articles

Impact of electron-phonon interactions on phonon transport in diamond and c-BN

Diamond and cubic polymorph of boron nitride (c-BN) are two promising next-generation ultrawide bandgap semiconductor materials owning superior thermal properties. Although lattice vibration is the dominant mechanism of heat conduction in semiconductors, electron-phonon interactions exist and may affect phonon transport in doped semiconductors; yet such effects in wide bandgap materials have not received much attention. In this study, we explore the effects of electron-phonon interactions on the lattice thermal conductivity and phonon transport in electron-doped Si, diamond, and c-BN under various electron concentrations and in a wide temperature range from 300 K to 900 K based on the first-principles calculation. It is found that the electron-phonon interactions will bring down the thermal conductivity of doped materials, and the depletion impact increases as the electron concentration increases but decreases as the temperature increases. This depression effect in ultrawide bandgap diamond and c-BN is apparent, though it is not as severe as in Si. At room temperature with a high electron concentration of 10 21 cm −3 , the reduction of thermal conductivity reaches 36 % in Si, and 17.4 % and 16.1 % in diamond and c-BN, respectively. • Thermal effect of electron-phonon interactions in doped c-BN and diamond is revealed. • Temperature and electron concentration dependent lattice thermal conductivity is quantified. • Thermal depletions exist in doped c-BN and diamond, but not as severe as in doped Si. • Depletion lessens as temperature rises, but increases with increasing electron concentration. • Ultrawide bandgap materials have great potentials in high-power high-temperature electronics.

Origin of abnormal thermal conductivity in group III-V boron compound semiconductors

Over the past half-century, according to Moore’s law, the sizes of transistors continue shrinking, and the integrated circuits have approached to their physical limits, which puts forward higher requirements for the thermal dissipation capacity of material. Revealing the physical mechanisms of heat conduction in semiconductors is important for thermal managements of devices. Experimentally, it was found that boron arsenide has a very high thermal conductivity compared with diamond, and boron arsenide has lattice constant close to silicon’s lattice constant, which can be heterogeneously integrated into silicon to solve the thermal management problem. However, group III-V boron compounds show abnormal thermal conductivities: the thermal conductivity of boron arsenide is significantly higher than that of boron phosphide and boron antimonide. Here, we use the first-principles calculation and the Boltzmann transport equation to study the thermal conductivity properties of the group III-V boron compounds. Comparison between the IV and III-V semiconductors shows that the high thermal conductivity of boron arsenide is due mainly to the existence of a large frequency gap between the acoustic and the optical branches. The energy sum of two acoustic phonons is less than energy of one optical phonon, which cannot meet the energy conservation requirements of three-phonon scattering, and then seriously restrict the probability of scattering of three phonons. The high thermal conductivity of diamond is due mainly to its great acoustic phonon group velocity. Although the boron phosphide also has a relatively large acoustic phonon group velocity, the frequency gap is relatively small, which cannot effectively suppress the three-phonon scattering, so the thermal conductivity of boron phosphide is less than that of boron arsenide. Although the frequency gap of boron antimonide is similar to that of boron arsenide, the thermal conductivity of boron antimonide is lower than that of boron arsenide due to its smaller acoustic phonon group velocity and larger coupling matrix element. The research provides a new insight into the design of semiconductor materials with high thermal conductivities.

Relativistic stable processes in quasiballistic heat conduction in semiconductors.

In this article, we show how relativistic α-stable processes can be used to explain quasiballistic heat conduction in semiconductors. This is a method that can fit experimental results of ultrafast laser heating in alloys. It also provides a connection to a rich literature on the Feynman-Kac formalism and random processes that transition from a stable Lévy process on short time and length scales to the Brownian motion at larger scales. This transition was captured by a heuristic truncated Lévy distribution in earlier papers. The rigorous Feynman-Kac approach is used to derive sharp bounds for the transition kernel. Future directions are briefly discussed.

Non-monotonic pressure dependence of the thermal conductivity of boron arsenide

Recent experiments demonstrate that boron arsenide (BAs) is a showcase material to study the role of higher-order four-phonon interactions in affecting heat conduction in semiconductors. Here we use first-principles calculations to identify a phenomenon in BAs and a related material - boron antimonide, that has never been predicted or experimentally observed for any other material: competing responses of three-phonon and four-phonon interactions to pressure rise cause a non-monotonic pressure dependence of thermal conductivity, κ, which first increases similar to most materials and then decreases. The resulting peak in κ shows a strong temperature dependence from rapid strengthening of four-phonon interactions relative to three-phonon processes with temperature. Our results reveal pressure as a knob to tune the interplay between the competing phonon scattering mechanisms in BAs and similar compounds, and provide clear experimental guidelines for observation in a readily accessible measurement regime.

Probing ballistic thermal conduction in segmented silicon nanowires.

Ballistic heat conduction in semiconductors is a remarkable but controversial nanoscale phenomenon, which implies that nanostructures can conduct thermal energy without dissipation. Here, we experimentally probed ballistic thermal transport at distances of 400-800 nm and temperatures of 4-250 K. Measuring thermal properties of straight and serpentine silicon nanowires, we found that at 4 K heat conduction is quasi-ballistic with stronger ballisticity at shorter length scales. As we increased the temperature, quasi-ballistic heat conduction weakened and gradually turned into diffusive regime at temperatures above 150 K. Our Monte Carlo simulations illustrate how this transition is driven by different scattering processes and linked to the surface roughness and the temperature. These results demonstrate the length and temperature limits of quasi-ballistic heat conduction in silicon nanostructures, knowledge of which is essential for thermal management in microelectronics.

Heat conduction in semiconductors

Heat conduction in semiconductors

Heat conduction in semiconductors

Heat conduction in semiconductors