Theoretical predicted high-thermal-conductivity cubic Si3N4 and Ge3N4: promising substrate materials for high-power electronic devices

Huimin Xiang,Zhongping Li,Yanchun Zhou,Zhihai Feng

doi:10.1038/s41598-018-32739-x

Abstract

Ceramic substrates play key roles in power electronic device technology through dissipating heat, wherein both high thermal conductivity and mechanical strength are required. The increased power of new devices has led to the replacement of Al2O3 by high thermal conducting AlN and further β-Si3N4 based substrates. However, the low mechanical strength and/or anisotropic mechanical/thermal properties are still the bottlenecks for the practical applications of these materials in high power electronic devices. Herein, using a combination of density functional theory and modified Debye-Callaway model, two new promising substrate materials γ-Si3N4 and γ-Ge3N4 are predicted. Our results demonstrate for the first time that both compounds exhibit higher room temperature thermal conductivity but less anisotropy in expansion and heat conduction compared to β-Si3N4. The mechanism underpins the high RT κ is identified as relatively small anharmonicity, high phonon velocity and frequency. The suitability of these two nitrides as substrate materials was also discussed.

Highlights

The growing consumption of energy and emission of greenhouse gas have great impact on our society
Γ-Si3N4 is attractive due to the isotropy in thermal expansion and conductivity endowed by its high structure symmetry, which makes it promising as an alternative ceramic substrate material in high power electronic devices
The Bravais lattice of an ideal spinel structure consists of a fcc sublattice of N with metal atoms occupying one eighth of the interstitial tetrahedral sites and one half of the octahedral sites[12]

Summary

Introduction

The growing consumption of energy and emission of greenhouse gas have great impact on our society. Search for new ceramic materials with better thermal and mechanical properties is eagerly awaited for the development of high power electronic devices. Γ-Si3N4 is attractive due to the isotropy in thermal expansion and conductivity endowed by its high structure symmetry, which makes it promising as an alternative ceramic substrate material in high power electronic devices. To gauge the suitability of using γ-Si3N4 as a new ceramic substrate in high power electronic devices, in this contribution, we attempt to predict the thermal transport property of this potential high thermal conductivity material and its analogue γ-Ge3N4, and link the heat conduction properties of these two nitrides to their structure characteristic. With the help of first principles calculations and modified Debye-Callaway model, the high thermal conductivity at room temperature of both nitrides is confirmed and the suitability of both compounds as substrate materials will be discussed

Methods

Results

Conclusion