Abstract Reducing the thermal stress induced in GaN crystals is key for the fabrication of large-diameter GaN crystals. In the Na-flux method, thermal stress is eliminated by sapphire dissolution at growth temperature after growth. We succeeded in fabricating a freestanding GaN substrate with this technique. However, the flux with Li used as a solvent to dissolve the sapphire can also dissolve the GaN. In this study, we demonstrate that increasing the amount of nitrogen can suppress GaN dissolution in the Li-added flux, without interfering in the dissolution of sapphire. This means that the sapphire and GaN have different dissolution mechanisms. By utilizing the different mechanisms, we succeeded in selectively dissolving sapphire and fabricating a 1.5-inch freestanding GaN substrate. It is revealed by secondary ion mass spectrometry (SIMS) that Li is incorporated in the crystal. The distribution of Li indicated that it was included in the crystal during sapphire dissolution.

中文翻译：

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通过在 Na 助熔剂生长后使用 Li 选择性溶解蓝宝石来制造 1.5 英寸独立式 GaN 衬底

摘要 降低GaN晶体中引起的热应力是制备大直径GaN晶体的关键。在 Na-flux 方法中，通过在生长后在生长温度下溶解蓝宝石来消除热应力。我们成功地用这种技术制造了一个独立的 GaN 衬底。然而，以锂为溶剂溶解蓝宝石的助熔剂也可以溶解氮化镓。在这项研究中，我们证明增加氮的量可以抑制添加锂的助熔剂中 GaN 的溶解，而不会干扰蓝宝石的溶解。这意味着蓝宝石和 GaN 具有不同的溶解机制。通过利用不同的机制，我们成功地选择性溶解蓝宝石并制造了 1.5 英寸的独立式 GaN 衬底。二次离子质谱法 (SIMS) 表明，Li 结合在晶体中。Li 的分布表明它在蓝宝石溶解过程中包含在晶体中。