A comprehensive review is given over the state-of-the-art in the growth of zinc oxide (ZnO) and gallium nitride (GaN) by solvothermal technologies. Using solvothermal approaches also marks a new era in the technology of semiconductor crystal growth since for the first time a supercritical solvent is being employed for mass-production. Previously demonstrated were the hydrothermal growth of a three-inch size (0001) ZnO crystal by Tokyo Denpa and, more recently, the first successful ammonothermal growth of GaN on a one-inch size (0001) GaN seed crystal. We report on recent achievements including solubility of GaN, and give an outlook for the growth of large-size GaN crystal by the ammonothermal route. Complementary to the hydrothermal growth of ZnO fabrication of highly crystalline ZnO films by liquid phase epitaxy is discussed as a route for fast-screening of properties of doped ZnO crystals fabricated under conditions of thermodynamic equilibrium.
The scientific and technological backgrounds for the growth method of dislocation-free Czochralski silicon crystals without thin necks is introduced, and the development of the neckless growth method is reviewed. Robust silicon wafers which are heavily co-doped with B and Ge are also introduced in the relationship to impurity hardening effect. Finally, more advanced studies on the neckless growth method and robust silicon wafers are briefly introduced from the viewpoint of the industrial establishment.