Yu Xiaotong, Li Yifan, He Renjie, Wen Yanwei, Chen Rong, Xu Baoxing, Gao Yuan
State Key Laboratory of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, China.
State Key Laboratory of Material Processing and Die and Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, Hubei, 430074, China.
Nanoscale Horiz. 2024 Aug 19;9(9):1557-1567. doi: 10.1039/d4nh00245h.
Gallium nitride offers an ideal material platform for next-generation high-power electronics devices, which enable a spectrum of applications. The thermal management of the ever-growing power density has become a major bottleneck in the performance, reliability, and lifetime of the devices. GaN/diamond heterostructures are usually adopted to facilitate heat dissipation, given the extraordinary thermal conduction properties of diamonds. However, thermal transport is limited by the interfacial conductance at the material interface between GaN and diamond, which is associated with significant mechanical stress at the atomic level. In this work, we investigate the effect of mechanical strain perpendicular to the GaN/diamond interface on the interfacial thermal conductance of heterostructures using full-atom non-equilibrium molecular dynamics simulations. We found that the heterostructure exhibits severe mechanical stress at the interface in the absence of loading, which is due to lattice mismatch. Upon tensile/compressive loading, the interfacial stress is more pronounced, and the strain is not identical across the interface owing to the contrasting elastic moduli of GaN and diamond. In addition, the interfacial thermal conductance can be notably enhanced and suppressed by tensile and compressive strains, respectively, leading to a 400% variation in thermal conductance. More detailed analyses reveal that the change in interfacial thermal conductance is related to the surface roughness and interfacial bonding strength, as described by a generalized relationship. Moreover, phonon analyses suggest that the unequal mechanical deformation under compressive strain in GaN and diamond induces different frequency shifts in the phonon spectra, leading to an enhancement in phonon overlapping energy, which promotes phonon transport at the interface and elevates the thermal conductance and for tensile strain. The effect of strain on interface thermal conductance was investigated at various temperatures. Based on the mechanical tunability of thermal conductance, we propose a conceptual design for a mechanical thermal switch that regulates thermal conductance with excellent sensitivity and high responsiveness. This study offers a fundamental understanding of how mechanical strain can adjust interface thermal conductance in GaN/diamond heterostructures with respect to mechanical stress, deformation, and phonon properties. These results and findings lay the theoretical foundation for designing thermal management devices in a strain environment and shed light on developing intelligent thermal devices by leveraging the interplay between mechanics and thermal transport.
氮化镓为下一代高功率电子器件提供了一个理想的材料平台，这些器件具有一系列应用。不断增长的功率密度的热管理已成为器件性能、可靠性和寿命的主要瓶颈。鉴于金刚石具有非凡的热传导特性，通常采用氮化镓/金刚石异质结构来促进散热。然而，热传输受到氮化镓和金刚石之间材料界面处的界面热导的限制，这与原子水平上的显著机械应力有关。在这项工作中，我们使用全原子非平衡分子动力学模拟研究垂直于氮化镓/金刚石界面的机械应变对异质结构界面热导的影响。我们发现，在没有加载的情况下，异质结构在界面处表现出严重的机械应力，这是由于晶格失配。在拉伸/压缩加载时，界面应力更加明显，并且由于氮化镓和金刚石的弹性模量不同，整个界面的应变并不相同。此外，拉伸和压缩应变分别可以显著提高和抑制界面热导，导致热导变化400%。更详细的分析表明，界面热导的变化与表面粗糙度和界面结合强度有关，如一个广义关系所描述。此外，声子分析表明，氮化镓和金刚石在压缩应变下的不等机械变形会在声子谱中引起不同的频移，导致声子重叠能量增加，从而促进界面处的声子传输并提高热导，而拉伸应变则相反。在不同温度下研究了应变对界面热导的影响。基于热导的机械可调性，我们提出了一种机械热开关的概念设计，该开关以优异的灵敏度和高响应性调节热导。这项研究提供了关于机械应变如何相对于机械应力、变形和声子特性来调节氮化镓/金刚石异质结构中的界面热导的基本理解。这些结果和发现为在应变环境中设计热管理器件奠定了理论基础，并为通过利用力学和热传输之间的相互作用开发智能热器件提供了启示。
