Growth of High Crystalline Quality HVPE-GaN Crystals with Controlled Electrical Properties

Thick free-standing hydride vapor phase epitaxy (HVPE) GaN wafers were grown with close to perfect crystalline quality and with more than two orders of magnitude reduced free carrier concentration relative to ammonothermal GaN without resorting to deep level compensation. These new homoepitaxially grown crystals exceed the quality of any commercially available GaN substrates. High crystalline quality is confirmed by XRD rocking curve measurements having full width at half-maximum of only 16 arc s. Detailed Raman scattering spectroscopy and imaging show that the wafers are biaxially stress-free and have a uniform and low background doping. The stress-free, flat nature of these substrates is essential for high-yield device fabrication. High-resolution photoluminescence studies in combination with SIMS analysis identify Si and O as residual shallow donors with concentration levels orders of magnitude lower than those present in ammonothermal GaN substrates.