Self-separation of two-inch-diameter freestanding GaN by hydride vapor phase epitaxy and heat treatment of sapphire

• A new simple method is introduced for obtaining freestanding GaN.
• A new phenomenon called delamination inside GaN layer was observed.
• The critical thickness of full delamination was presented according to a new model.
• As-fabricated two-inch-diameter freestanding GaN proved to be with high quality.

In this letter, a new simple method is introduced for obtaining freestanding GaN. The method combines hydride vapor phase epitaxy and heat-treatment of sapphire, which has been implemented to improve mechanical properties before the growth of GaN template by metalorganic chemical vapor deposition. After hydride vapor phase epitaxy on the GaN template, spontaneous separation took place inside the GaN layer at room temperature, in which process, a new phenomenon called delamination inside GaN layer was observed. The delamination was believed to be driven by the large thermal mismatch stress and the interface shear stress at the wafer edge. Two-inch-diameter freestanding GaN with high quality was thus obtained. The full width at half maximum for X-ray rocking curve were about 108 and 81 arcs for (0 0 2) and (1 0 2) reflections. The dislocation density of the freestanding GaN was about 3–7×106 cm−2.