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<p>Efficient thermal management remains a critical challenge for high-power GaN-based electronic devices, where excessive self-heating severely limits performance and reliability. In this work, a GaN-on-diamond structure employing an ultra-thin AlN interlayer is systematically investigated to reduce interfacial thermal boundary resistance (TBR) and improve interface stability. A 5&#xa0;nm-thick AlN film was deposited on the GaN surface as an interfacial transition layer, followed by diamond film growth via microwave plasma chemical vapor deposition (MPCVD) using a rapid nucleation–slow growth (RNSG) process. To elucidate the role of both interlayer material and growth strategy, diamond films grown on AlN and SiN<sub><i>X</i></sub> interlayers were comparatively studied under single-stage growth and RNSG conditions. The surface morphology, cross-sectional structure, and crystalline quality of the diamond films were characterized using scanning electron microscopy (SEM), Raman spectroscopy, and x-ray diffraction (XRD), while the interfacial thermal transport properties were quantitatively evaluated by transient thermoreflectance (TTR). The results demonstrate that the 5&#xa0;nm AlN interlayer combined with the RNSG process significantly enhances diamond nucleation behavior, leading to a higher nucleation density, improved grain uniformity, and a pronounced (220) preferred orientation. Cross-sectional observations reveal a dense, void-free diamond seed layer and a well-bonded GaN/diamond interface, indicating effective suppression of interfacial defects and weakly bonded regions. As a consequence, the measured TBR exhibits enhanced stability and reproducibility, with values concentrated in a narrow range of approximately 26 m<sup>2</sup>·K/GW, which is markedly lower and more consistent than those obtained from reference samples employing a 30&#xa0;nm SiN<sub><i>X</i></sub> interlayer. These findings suggest that the 5&#xa0;nm AlN interlayer provides an optimal balance between interface continuity, mechanical robustness, and phonon coupling efficiency, while the RNSG process further promotes high-quality diamond growth at the early nucleation stage. This work establishes a robust interfacial engineering strategy for constructing low-TBR, high-stability GaN-on-diamond heterostructures, offering a viable pathway toward advanced thermal management in next-generation high-power GaN devices.</p>

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RNSG-Assisted Growth of Diamond on GaN Using Ultrathin AlN Interlayers

  • 期刊论文

  • 发表日期：

    2026年4月10日

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  • Caie He,
  • Jiahao Yao,
  • Qian Fan,
  • Xianfeng Ni,
  • Xing Gu

摘要

Efficient thermal management remains a critical challenge for high-power GaN-based electronic devices, where excessive self-heating severely limits performance and reliability. In this work, a GaN-on-diamond structure employing an ultra-thin AlN interlayer is systematically investigated to reduce interfacial thermal boundary resistance (TBR) and improve interface stability. A 5 nm-thick AlN film was deposited on the GaN surface as an interfacial transition layer, followed by diamond film growth via microwave plasma chemical vapor deposition (MPCVD) using a rapid nucleation–slow growth (RNSG) process. To elucidate the role of both interlayer material and growth strategy, diamond films grown on AlN and SiNX interlayers were comparatively studied under single-stage growth and RNSG conditions. The surface morphology, cross-sectional structure, and crystalline quality of the diamond films were characterized using scanning electron microscopy (SEM), Raman spectroscopy, and x-ray diffraction (XRD), while the interfacial thermal transport properties were quantitatively evaluated by transient thermoreflectance (TTR). The results demonstrate that the 5 nm AlN interlayer combined with the RNSG process significantly enhances diamond nucleation behavior, leading to a higher nucleation density, improved grain uniformity, and a pronounced (220) preferred orientation. Cross-sectional observations reveal a dense, void-free diamond seed layer and a well-bonded GaN/diamond interface, indicating effective suppression of interfacial defects and weakly bonded regions. As a consequence, the measured TBR exhibits enhanced stability and reproducibility, with values concentrated in a narrow range of approximately 26 m2·K/GW, which is markedly lower and more consistent than those obtained from reference samples employing a 30 nm SiNX interlayer. These findings suggest that the 5 nm AlN interlayer provides an optimal balance between interface continuity, mechanical robustness, and phonon coupling efficiency, while the RNSG process further promotes high-quality diamond growth at the early nucleation stage. This work establishes a robust interfacial engineering strategy for constructing low-TBR, high-stability GaN-on-diamond heterostructures, offering a viable pathway toward advanced thermal management in next-generation high-power GaN devices.