Gallium nitride bulk crystal growth processes: A review

Optoelectrical and microelectronic devices involving gallium nitride have become a challenge but their development is limited because of a lack of suitable substrates. This paper deals with the crystal growth of gallium nitride, the processes leading to GaN bulk crystals being significantly expanded during the last decade (the ones involving GaN thin films or nanocrystallites are not studied in this review). The main reviewed routes are: (i) the high pressure nitrogen solution growth (H.P.N.S.G.), (ii) the Na flux method, and (iii) the ammonothermal crystal growth.