  Polymorphs are common in nature and can be stabilized by applying external
pressure in materials. The pressure/strain can also be induced by the gradually
accumulated radiation disorder. However, in semiconductors, the radiation
disorder accumulation typically results in the amorphization instead of
engaging polymorphism. By studying these phenomena in gallium oxide we found
that the amorphization may be prominently suppressed by the monoclinic to
orthorhombic phase transition. Utilizing this discovery, a highly oriented
single-phase orthorhombic film on the top of the monoclinic gallium oxide
substrate was fabricated. Exploring this system, a novel mode of a lateral
polymorphic regrowth, not previously observed in solids, was detected. In
combination, these data envisage a new direction of research on polymorphs in
Ga2O3 and, potentially, for similar polymorphic families in other materials.
