Abstract We demonstrate the achieving of high-quality AlN films on flat sapphire substrate (FSS) by introducing voids during growth. Voids are embedded into AlN epilayers through a growth-mode transition from island growth to step flow growth. Such voids significantly facilitated the underlying dislocations annihilation as demonstrated by the transmission electron microscopy (TEM) image. For the 3 μm-thick AlN film grown on FSS, the full width at half maximum of the X-ray rocking curve was 57/260 arcsec for (0 0 2)/(1 0 2) reflection and a threading dislocation density of 1.7 × 108 cm−2 was determined from plain-view TEM image. Moreover, the voids provided an additional stress relief channel in the AlN film grown on FSS, resulting in a tensile stress comparable to that of grown on nano-patterned sapphire substrate (NPSS). The measured lattice constants and Raman shift of AlN-E2 (high) peak verified the 3 μm-thick AlN film grown on FSS is nearly stress free at room temperature. Taking advantages of the deliberately embedded voids, a crack-free and atomically flat AlN film was grown on FSS. The strategy put forward in this work to obtaining high-quality AlN films on FSS is much cost-efficient, which is believed to hold great promise for commercialization in AlN-based devices.

中文翻译：

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通过生长模式修改引入空隙，在蓝宝石衬底上生长高质量的 AlN 薄膜

摘要 我们展示了通过在生长过程中引入空隙，在平面蓝宝石衬底 (FSS) 上实现高质量 AlN 薄膜。通过从岛状生长到阶梯流生长的生长模式转变，空隙被嵌入到 AlN 外延层中。如透射电子显微镜 (TEM) 图像所示，这种空隙显着促进了潜在的位错湮灭。对于在 FSS 上生长的 3 μm 厚的 AlN 薄膜，对于 (0 0 2)/(1 0 2) 反射和穿透位错密度为 1.7 的 X 射线摇摆曲线的半峰全宽为 57/260 弧秒× 108 cm-2 由平视 TEM 图像确定。此外，空隙在 FSS 上生长的 AlN 膜中提供了一个额外的应力释放通道，导致拉伸应力与在纳米图案蓝宝石衬底 (NPSS) 上生长的拉伸应力相当。测量的 AlN-E2（高）峰的晶格常数和拉曼位移证实了在 FSS 上生长的 3 μm 厚的 AlN 膜在室温下几乎没有应力。利用故意嵌入的空隙，在 FSS 上生长无裂纹且原子级平坦的 AlN 薄膜。在这项工作中提出的在 FSS 上获得高质量 AlN 薄膜的策略具有很高的成本效益，这被认为对基于 AlN 的设备的商业化具有很大的希望。