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首页> 外文期刊>Journal of Crystal Growth >Formation of large-area freestanding gallium nitride substrates by natural stress-induced separation of GaN and sapphire
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Formation of large-area freestanding gallium nitride substrates by natural stress-induced separation of GaN and sapphire

机译：通过自然应力诱导的GaN和蓝宝石的分离形成大面积的独立氮化镓衬底

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This paper addresses the formation of freestanding GaN substrates by a natural separation mechanism, effectively eliminating the need for post-growth processes such as laser liftoff, chemical etching or mechanical lapping to form freestanding GaN substrates. A number of GaN thick films were grown onto sapphire substrates by the hydride vapor-phase epitaxy (HVPE) method with thickness varying from 200 μm to 3.8 mm using either a low-temperature GaN or an AlN buffer as the nucleation step. We have found that samples grown on a low temperature GaN buffer naturally delaminate from the sapphire substrate post-growth over the entire thickness range studied. Furthermore, we have observed that the thinner films have high crack densities leading to the delamination of several smaller freestanding pieces. As the GaN thickness increases, the area of the delaminated pieces also increases, ultimately leading to a 1-to-1 correlation between initial sapphire substrate area and freestanding GaN area. However, the GaN films grown on AlN buffers did not delaminate. These results were accounted for by calculating the thermal stresses in the GaN film and substrate as a function of film thickness using Stoney's equation and assuming that the GaN buffer undergoes decomposition at the growth temperature.
机译：本文探讨了通过自然分离机制形成独立式GaN衬底的方法，有效消除了对后生长工艺（例如激光剥离，化学蚀刻或机械研磨）以形成独立式GaN衬底的需求。通过氢化物气相外延（HVPE）方法，使用低温GaN或AlN缓冲液作为成核步骤，将多种GaN厚膜生长在蓝宝石衬底上，厚度从200μm到3.8 mm不等。我们发现，在整个研究的整个厚度范围内，在低温GaN缓冲液上生长的样品自然地会从蓝宝石衬底上脱层。此外，我们已经观察到，较薄的薄膜具有较高的裂纹密度，从而导致多个较小的独立部件分层。随着GaN厚度的增加，分层件的面积也增加，最终导致初始蓝宝石衬底面积与独立式GaN面积之间存在1：1的相关性。但是，在AlN缓冲层上生长的GaN膜并未分层。通过使用Stoney方程计算GaN膜和衬底中的热应力作为膜厚度的函数，并假设GaN缓冲液在生长温度下发生分解，可以解释这些结果。

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