We report the growth of a 3.5 mm-thick bulk GaN layer using a stress-engineered homoepitaxy method without any external processes. We employ a gradient V/III ratio during the growth, which enables a 3.5 mm-thick bulk GaN layer with a smooth surface and high crystal quality to be obtained. For a constant V/III ratio of 10, the bulk GaN layer has a flat surface; however, microcracks emerge in the GaN layer. For a constant V/III ratio of 38, the bulk GaN layer has a rough surface, without microcracks. On the other hand, by decreasing the V/III ratio from 38 to 10, the structural properties of the GaN layers are successfully controlled. The higher V/III ratio in the initial growth stage leads to a rough surface, and reduced stress and dislocation density in the bulk GaN layers, while the lower V/III ratio in the second stage of the growth provides an opposite trend, confirmed by Raman spectroscopy and X-ray measurements. We expect that this study will offer a new opportunity to achieve the growth of high-crystallinity bulk GaN without ex situ and complicated processes.

中文翻译：

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使用氢化物​​气相外延的同质外延 GaN 晶体的应力工程生长

我们报告了使用应力工程同质外延方法生长 3.5 mm 厚的体 GaN 层，而无需任何外部工艺。我们在生长过程中采用梯度 V/III 比率，这使得能够获得具有光滑表面和高晶体质量的 3.5 mm 厚的块体 GaN 层。对于 10 的恒定 V/III 比，体 GaN 层具有平坦的表面；然而，在 GaN 层中会出现微裂纹。对于 38 的恒定 V/III 比率，体 GaN 层具有粗糙表面，没有微裂纹。另一方面，通过将 V/III 比率从 38 降低到 10，成功地控制了 GaN 层的结构特性。初始生长阶段较高的 V/III 比会导致表面粗糙，并降低体 GaN 层中的应力和位错密度，而在生长的第二阶段较低的 V/III 比率则提供了相反的趋势，这已通过拉曼光谱和 X 射线测量得到证实。我们预计这项研究将为实现高结晶体 GaN 的生长提供一个新的机会，而无需异地和复杂的过程。