A QUARTZ-LIKE MATERIAL - GALLIUM PHOSPHATE (GAPO4) - CRYSTAL-GROWTH AND CHARACTERIZATION

This investigation concerns GaPO4 crystal growth in sulphuric and phos phoric acid media through the slow heating and vertical reverse temper ature gradient methods. Systematic study of growth parameters shows th at the growth rate V(x) is always much greater than the two other ones , V(z) and V(y). The most interesting result is the ability to produce GaPO4 epitaxy on large berlinite seeds in sulphuric acid and to use t hem for GaPO4 CryStal growth in phosphoric acid. The epitaxial fit and the crystalline quality have been checked by X-ray topography. The [O H] content, determined by infrared spectrometry, seems to prove a lowe r OH concentration than in case of berlinite when approximatively the same crystal growth conditions are used. First piezoelectric character izations for resonators near the AT cut show GaPO4 to be a very promis ing piezoelectric material with a large coupling coefficient near 16%, a quartz-like thermal stability and a Q factor already nearly suffici ent for the applications.