Plastic Relaxation without Dislocations in $β$-Ga$_2$O$_3$ Heteroepitaxy: A Structural Peculiarity of Ga$_2$O$_3$ Polymorphs

$β$-Ga$_2$O$_3$ grows as three-dimensional islands on mismatched c-plane sapphire, often on a thin $α$-Ga$_2$O$_3$ wetting layer, and eventually forms a continuous film by island coalescence.

$β$-Ga$_2$O$_3$ grows as three-dimensional islands on mismatched c-plane sapphire, often on a thin $α$-Ga$_2$O$_3$ wetting layer, and eventually forms a continuous film by island coalescence. Experiments reveal the $β$ film to be relaxed. Surprisingly no dislocations are…