Abstract
The bulk thermal conductivity of Stillinger-Weber (SW) wurtzite GaN in the [0001] direction at a temperature of 300 K is calculated using equilibrium molecular dynamics (EMD), non-equilibrium MD (NEMD), and lattice dynamics (LD) methods. While the NEMD method predicts a thermal conductivity of 166 ± 11 W/m·K, both the EMD and LD methods predict thermal conductivities that are an order of magnitude greater. We attribute the discrepancy to significant contributions to thermal conductivity from long-mean free path phonons. We propose that the Grüneisen parameter for low-frequency phonons is a good predictor of the severity of the size effects in NEMD thermal conductivity prediction. For weakly anharmonic crystals characterized by small Grüneisen parameters, accurate determination of thermal conductivity by NEMD is computationally impractical. The simulation results also indicate the GaN SW potential, which was originally developed for studying the atomic-level structure of dislocations, is not suitable for prediction of its thermal conductivity.
Highlights
Due to its electronic and thermal transport properties, GaN is an important component in microelectronic devices such as LEDs, laser diodes, and high electron mobility transistors.1–6 Its high thermal conductivity is crucial for efficient heat dissipation in high-power GaN-based microelectronics
The defect density in GaN crystals has been significantly reduced in the past decade,7–12 it is still several orders of magnitude greater than that in typical silicon wafers
We evaluate the validity of the linear extrapolation procedure for non-equilibrium MD (NEMD) prediction of k and assess the suitability of the existing SW potential18 for quantitative modeling of thermal transport in GaN
Summary
Due to its electronic and thermal transport properties, GaN is an important component in microelectronic devices such as LEDs, laser diodes, and high electron mobility transistors. Its high thermal conductivity is crucial for efficient heat dissipation in high-power GaN-based microelectronics. Due to its electronic and thermal transport properties, GaN is an important component in microelectronic devices such as LEDs, laser diodes, and high electron mobility transistors.. Its high thermal conductivity is crucial for efficient heat dissipation in high-power GaN-based microelectronics. The room-temperature thermal conductivity, k, along the [0001] direction of single-crystal wurtzite GaN reported in experiments varies from 170 to 250 W/mÁK. The GaN crystals used in experiments contain a variety of defects such as dislocations, impurities, and isotopes. We determine k of the perfect GaN wurtzite crystal along the [0001] direction using EMD, NEMD, and LD methods.
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