Growth and properties of freestanding GaN substrates by HVPE using an AlN buffer layer deposited on Si

A hydride vapor-phase epitaxy (HVPE) method was employed to grow a thick Ga N film on an AlN buffer layer deposited a Si substrate, and the subsequent chemical removal of the sacrificial Si substrate resulted in the freestandi ng GaN substrates without cracks, having a present maximum area of 10x10 mm (2) and a thickness of 350 mu m. The freestanding GaN substrates had a high ly c-axis-oriented polycrystalline phase. The photoluminescence spectrum (a t 10 K) showed a bound exciton-related emission and a deep-level transition at 1.85 eV. The carrier concentration and the Hall mobility were 1.3x10(18 ) cm(-3) and 42.3 cm(2)/Vsec, respectively, at room temperature. The freest anding and crack-free GaN substrates prepared through this work can be used for homoepitaxial growth of GaN-based optoelectronic devices.