[论文解读] Thermal Conductance across beta-Ga2O3-diamond Van der Waals Heterogeneous Interfaces

Zhe Cheng, Luke Yates+4 more|arXiv (Cornell University)|Jan 9, 2019

Ga2O3 and related materials参考文献 36被引用 5

一句话总结

本研究测量了机械剥离的β-Ga₂O₃纳米膜与单晶金刚石衬底之间范德华异质结的热边界导纳（TBC），测得TBC为17 MW/m²K，与金属-金刚石界面相当。通过基于Landauer的声子输运模型，研究揭示了界面声子散射和膜边界效应的作用，为优化基于Ga₂O₃的功率器件热管理提供了洞见。

ABSTRACT

Because of its ultrawide bandgap, high breakdown electric field, and large area affordable substrates grown from the melt, beta Ga2O3 has attracted great attention recently for potential applications of power electronics. However, its thermal conductivity is significantly lower than those of other wide bandgap semiconductors, such as AlN, SiC, GaN, and diamond. To ensure reliable operation with minimal selfheating at high power, proper thermal management is even more essential for Ga2O3 devices. Similarly to the past approaches aiming to alleviate selfheating in GaN HEMTs, a possible solution has been to integrate thin Ga2O3 membranes with diamond to fabricate Ga2O3 on diamond lateral MESFET or MOSFET devices by taking advantage of the ultra high thermal conductivity of diamond. Even though the TBC between wide bandgap semiconductor devices such as GaN HEMTs and a diamond substrate is of primary importance for heat dissipation in these devices, fundamental understanding of the Ga2O3 diamond thermal interface is still missing. In this work, we study the thermal transport across the interfaces of Ga2O3 exfoliated onto a single crystal diamond. The Van der Waals bonded Ga2O3 diamond TBC is measured to be 17 MWm2K1, which is comparable to the TBC of several physical vapor deposited metals on diamond. A Landauer approach is used to help understand phonon transport across perfect Ga2O3 diamond interface, which in turn sheds light on the possible TBC one could achieve with an optimized interface. A reduced thermal conductivity of the Ga2O3 nanomembrane is also observed due to additional phonon membrane boundary scattering. The impact of the Ga2O3substrate TBC and substrate thermal conductivity on the thermal performance of a power device are modeled and discussed.

研究动机与目标

• 研究β-Ga₂O₃-金刚石范德华异质结的热输运特性，以支持功率电子应用。
• 量化Ga₂O₃-金刚石界面的热边界导纳（TBC），这是热管理的关键参数。
• 理解界面声子散射和膜边界效应对Ga₂O₃纳米膜热导率的影响。
• 建立模型，分析衬底热导率和TBC对Ga₂O₃基功率器件热性能的影响。
• 基于Landauer方法提供理论框架，预测最优界面工程以实现更高效的散热。

提出的方法

• 将机械剥离的单晶β-Ga₂O₃纳米膜转移到高质量单晶金刚石衬底上，形成范德华异质结。
• 采用时域热反射法（TDTR）实验测量Ga₂O₃-金刚石界面的热边界导纳。
• 应用基于Landauer的声子输运模型，模拟理想化Ga₂O₃-金刚石界面的声子透射行为。
• 考虑声子模式和界面耦合，估算本征TBC极限并识别关键散射机制。
• 采用有限元建模方法，评估不同衬底热导率和TBC下Ga₂O₃器件的热性能。
• 对实验数据进行膜厚和边界散射效应的修正，以分离界面热阻。

实验结果

研究问题

• RQ1 β-Ga₂O₃-金刚石范德华界面的热边界导纳是多少？
• RQ2 Ga₂O₃-金刚石界面的声子输运性能与金属-金刚石体系相比如何？
• RQ3 界面散射和边界散射机制在多大程度上降低了Ga₂O₃纳米膜的热导率？
• RQ4 在优化的Ga₂O₃-金刚石界面处，热导率的理论上限是多少？
• RQ5 衬底热导率和界面导纳如何共同影响Ga₂O₃基功率器件的热性能？

主要发现

• 测得β-Ga₂O₃-金刚石范德华界面的热边界导纳（TBC）为17 MW/m²K。
• 该TBC值与物理气相沉积金属在金刚石上的值相当，表明尽管为范德华键合，界面仍具有较强的声子耦合。
• 由于膜表面声子散射增强，观察到Ga₂O₃纳米膜的热导率降低。
• Landauer模型预测的本征TBC高于实测值，表明实际系统中界面缺陷或粗糙度限制了性能。
• 热阻建模表明，衬底热导率和界面TBC均显著影响器件自加热效应，其中TBC在高功率工作条件下起主导作用。
• 优化界面质量可使Ga₂O₃-金刚石异质结实现适用于下一代功率电子器件的热性能。