Bulk GaN crystal growth by the high-pressure ammonothermal method

The rapidly growing gallium nitride device industry continues to be in dire need of high quality, cost effective native substrates. Considerable progress has been made with pseudo-bulk substrates synthesized by hydride vapor phase epitaxy (HVPE), but true bulk methods promise both superior quality and reduced cost. We give an overview of the high-pressure ammonothermal method developed by GE, based on adaptation of high-pressure apparatus developed for diamond growth, together with appropriate raw materials and methods. We describe recent progress, including characterization of and reductions in impurity concentrations, wafering, and successful fabrication of homoepitaxial laser diodes on GE substrates.