Growth of a Two-Inch GaN Single Crystal Substrate Using the Na Flux Method

We succeeded in growing a GaN single crystal substrate with diameter of about two inches using the Na flux method. Our success is due to the development of a new apparatus for growing large GaN single crystals. The crystal grown in this study has a low dislocation density of 2.3 × 10 5 cm -2 . The secondary ion mass spectrometry (SIMS) technique demonstrates that the Na element is difficult to be taken in the crystal in both the "+" and "-" c directions, resulting in a Na concentration of 4.2 × 10 14 cm -3 in the crystal. Our success in growing a two-inch GaN substrate with a low impurity content and low dislocation density should pave the way for the Na flux method to become a practical application.