Hydrothermal liquid phase epitaxy of gallium orthophosphate on quartz crystal substrates

Gallium orthophosphate (GaPO4) layers for surface acoustic wave (SAW) and s ensor applications have been grown on quartz crystal substrates with sizes of about 30 x 30 mm(2) by hydrothermal liquid phase epitaxy (HLPE). The gro wth of epitaxial GaPO4 layers is difficult because of a strong tendency for twinning. Besides, a retrograde solubility and an intense chemical aggress iveness of the solution has to be considered. Nevertheless, we found an eff ective crystal growth technique to deal with these problems using large and qualitatively good substrate crystals of quartz. The most important step o f the epitaxy is the formation of an interlayer between the quartz substrat e and the GaPO4 deposit. Epitaxial layers with thickness up to 500 mum were obtained and characterised by means of X-ray techniques.