Characterization of the Interfacial Toughness in a Novel "GaN-on-Diamond" Material for High-Power RF Devices
Characterization of the Interfacial Toughness in a Novel "GaN-on-Diamond" Material for High-Power RF Devices
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DOI：
10.1021/acsaelm.8b00091
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发表时间：
2019-03-01
影响因子：
4.7
通讯作者：
Kuball, Martin
中科院分区：
文献类型：
--
作者：
Liu, Dong;Fabes, Stephen;Kuball, Martin
集成在多晶金刚石衬底上的GaN薄膜是一种新型的微波晶体管材料，具有显著改善的散热能力。由于GaN和金刚石之间的热和机械性能不匹配，就其界面稳定性而言自然会引起关注，因为目前还没有确定的方法来评估GaN-金刚石材料中的界面韧性。使用三代不同工艺参数的“GaN-on-Diamond”材料，进行了全面的研究，以确定最合适的基于断裂力学的方法，用于可靠地评估这种新型材料系统中的界面韧性。几种技术进行了评估，结果进行了交叉比较，其中包括一个异位纳米压痕诱导屈曲方法和两步压痕方法连同几个分析模型。此外，采用微悬臂梁弯曲法测量了界面断裂韧性的上限。对于三代材料，界面韧性G（Ic）分别为0.7、0.9和0.6 J.m（-2）。断裂界面的微观和纳米结构的事后分析表明，具有更好的散热能力的系统显示出更光滑的断裂表面，即，由于缺乏主动增韧机制而更脆。根据实验结果，提出了潜在的修改接口，以提高机械稳定性。
GaN thin film integrated to polycrystalline diamond substrates is a novel microwave transistor material with significantly improved heat dissipation capability. Due to the thermal and mechanical properties mismatch between GaN and diamond, a natural concern arises in terms of its interfacial stability as currently there is no established method to evaluate the interfacial toughness in GaN-on-diamond material. Using three generations of "GaN-on-Diamond" materials with varying process parameters, a comprehensive study has been carried out to identify the most appropriate fracture mechanics-based methods for reliable evaluation of the interfacial toughness in this novel material system. Several techniques were assessed, and the results are cross-compared; these include an ex situ nanoindentation induced buckling method and two-step indentation approach together with several analytical models. Additionally, a microcantilever bending method was adopted to measure an upper bound for the interfacial fracture toughness. For the three generations of materials, the interfacial toughness, G(Ic), was determined to be 0.7, 0.9, and 0.6 J.m(-2), respectively. Postmortem analysis of the micro- and nanostructure of fractured interfaces indicated that the systems with better heat spreading capability displayed smoother fracture surfaces, i.e., were more brittle due to the lack of active toughening mechanisms. Potential modifications to the interface for improved mechanical stability were proposed based on the experimental results.