True bulk GaN technology for high efficiency devices

As GaN device technologies confront the need to increase yield and performance metrics, expected material improvements will come from the use of lattice-matched substrates. There is a growing interest in utilizing low-defect density GaN substrates for certain high performance applications. Manufacturers who make use of true bulk substrates will have the first opportunity to achieve the theoretically predicted performance and reliability for GaN-based devices. This paper will outline the progress of bulk GaN crystal growth techniques, and compare their various merits and deficiencies. Solvothermal growth, flux growth, and vapor phase growth are the main contenders that must prove their ability to provide high quality material consistently and at a competitive price. To validate their claims, we will discuss issues such as wafer purity, defect density, lattice bending, growth rate, and reproducibility.