Growth of Freestanding Gallium Nitride (GaN) Through Polyporous Interlayer Formed Directly During Successive Hydride Vapor Phase Epitaxy (HVPE) Process

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The progress of nitride technology is widely limited and hindered by the lack of high-quality gallium nitride (GaN) wafers. Therefore, a large number of GaN epitaxial devices are grown on heterogeneous substrates. Although various additional treatments of substrate have been used to promote crystal quality, there is still plenty of room for its improvement, in terms of direct and continuous growth based on the hydride vapor phase epitaxy (HVPE) technique. Here, we report a three-step process that can be used to enhance the quality of GaN crystal by tuning V/III rate during successive HVPE process. In the growth, a metal-organic chemical vapor deposition (MOCVD) grown GaN on sapphire (MOCVD-GaN/Al2O3) was employed as substrate, and a high-quality GaN polyporous interlayer, with successful acquisition, without any additional substrate treatment, caused the growth stress to decrease to 0.06 GPa. Meanwhile the quality of GaN improved, and the freestanding GaN was directly obtained during the growth process.