发表机构
University of Virginia; National Laboratory of the Rockies（弗吉尼亚大学; 落基山国家实验室）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用铟催化分子束外延在beta-Ga2O3衬底上生长(010) (AlxGa1-x)2O3薄膜，通过抑制缺陷和相分离将热导率提升2倍，并揭示合金散射主导热输运及界面热导随Al组分变化的机制。
AI 中文摘要
(AlxGa1-x)2O3/beta-Ga2O3晶体管是高性能和高频电子器件的新兴候选材料。特别是beta-Ga2O3，其各向异性的低热导率显著受限，而在(AlxGa1-x)2O3中，由于合金及其他缺陷引起的声子散射机制，热导率进一步降低。在本工作中，我们展示了通过时域热反射（TDTR）测量的(010)取向(AlxGa1-x)2O3薄膜（0.01 < x < 0.20）的热导率受合金散射限制，且未观察到额外缺陷带来的明显不利散射。这是通过在beta-Ga2O3衬底上利用分子束外延（MBE）合成(AlxGa1-x)2O3薄膜实现的，利用铟催化生长抑制位错形成和相分离，从而获得x高达0.2的单相赝晶薄膜。该生长工艺使(AlxGa1-x)2O3的热导率相较于先前报道值提高了2倍。随着Al组分（x）的增加，我们观察到(AlxGa1-x)2O3热导率因合金散射而持续下降，并通过虚晶近似（VCA）模型进行了验证。我们还展示了Al/(AlxGa1-x)2O3界面的热边界电导随x增加而降低，我们推测这是由于随着x增加，(AlxGa1-x)2O3声学模式变硬所致，并通过将实验结果与漫反射失配模型（DMM）进行比较来支持这一观点。总体而言，这些热特性为设计具有优化界面和组分的异质结构提供了宝贵的见解。
英文摘要
(AlxGa1-x)2O3/beta-Ga2O3 transistors are an emerging candidate for high-power and high-frequency electronic devices. beta-Ga2O3 in particular is notably limited for anisotropic low thermal conductivity, which is further reduced in (AlxGa1-x)2O3 due to alloy and other defect-driven phonon scattering mechanisms. In this work we show that the thermal conductivity of (010) oriented (AlxGa1-x)2O3 thin films for 0.01 < x < 0.20, measured using time-domain thermoreflectance (TDTR), is limited by alloy scattering without observable adverse scattering by additional defects. This is enabled through the synthesis of the (AlxGa1-x)2O3 films using molecular beam epitaxy (MBE) on \b{eta}-Ga2O3 substrates, leveraging indium-catalyzed growth to suppress dislocation formation and phase separation to achieve single-phase pseudomorphic films up to x = 0.2. This growth process improved the thermal conductivity of (AlxGa1-x)2O3 by 2X as compared to previously reported values. For increasing Al composition (x), we observe a steady decline in (AlxGa1-x)2O3 thermal conductivity due to alloy scattering which is validated using virtual crystal approximation (VCA) model. We also show that the thermal boundary conductance across the Al/(AlxGa1-x)2O3 interface is reduced with increasing x, which we posit is due to the stiffening of the (AlxGa1-x)2O3 acoustic modes with increasing x by comparing experimental results with a diffuse mismatch model (DMM). Overall, these thermal characteristics provide valuable insights for designing heterostructures with optimized interfaces and composition.
