Crystal growth and physical characterizations of GaPO4

An investigation concerning GaPO4 crystal growth in sulphuric and phosphoric acid media through the slow heating and vertical reverse temperature gradient methods is reported. Systematic study of growth parameters shows a Vx growth rate always much greater than the two other ones: Vz and Vy. The most interesting result is the ability to do GaPO4 epitaxy in large berlinite seems in sulphuric acid and, after that, to use them for GaPO4 crystal growth in phosphoric acid. The good epitaxy process and the crystalline quality were checked by x ray topography. The (OH) content, followed by infrared spectrometry, seems to prove a lower OH concentration than in the berlinite case for approximately the same crystal growth conditions. First piezoelectric characterizations of resonators near the AT cut show GaPO4 to be a very promising piezoelectric material with a large coupling coefficient near 16 percent, a quartz like thermal stability, and a Q factor already nearly sufficient for the applications.