Basic ammonothermal growth of Gallium Nitride - State of the art, challenges, perspectives

Recent progress in ammonothermal technology of bulk GaN growth in basic environment is presented and discussed in this paper. This method enables growth of two-inch in diameter crystals of outstanding structural properties, with radius of curvature above tens of meters and low threading dislocation density of the order of 5 x 10(4) cm(-2). Crystals with different types of conductivity, n-type with free electron concentration up to 10(19) cm(-3), p-type with free hole concentration of 10(16) cm(-3) and semi-insulating with resistivity exceeding 10(11) Omega cm, can be obtained. Ammonothermal GaN of various electrical properties is described in terms of point defects present in the material. Potential applications of high-quality GaN substrates are also briefly shown.