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With its wide bandgap and high critical field, GaN is a promising material for high power electronics. To date, most GaN films have been grown on foreign substrates such as sapphire or SiC. Lattice mismatch between the film and substrate leads to a large number of threading dislocations (~109 -1010 cm-2). These defects are thought to lead to poor device performance such as premature breakdown. Device properties are generally improved by growth of low-doped (<; 1016 cm-3) GaN layers on high conductivity freestanding hydride vapor phase epitaxy (HVPE) GaN substrates. However, these films still have a large number of dislocations ~ 106 cm-2. Dislocations are randomly oriented in both hetero and homoepitaxial films leading to a wide variation of material quality and thus device performance across the wafer. Recently, a true bulk GaN substrate became available using an ammonothermal growth technique. These substrates have both a low resistivity and low threading dislocation density. Growth of low-doped films on these bulk substrates can potentially address the problems of uniformity and premature breakdown in GaN power Schottky diodes.