19. Structural Properties 1

This chapter describes structural evaluation of β-Ga₂O₃ crystals grown by edge-defined film-fed growth process using etch pitting, focused ion beam scanning ion microscopy, transmission electron microscopy, and related techniques. Three types of defects have been found in the crystals. First, arrays of edge dislocations were observed corresponding to etch pit arrays on a \( (\bar{2}01) \)-oriented wafer after etching with hot H₃PO₄. In some of the dislocations, the line-shaped appearance is slightly deformed due to an inhomogeneous strain field. Next, platelike nanovoids which correspond to etch pits on the (010) plane were observed. Although the crystallographic configurations of the defects are different from that of nanometer-sized crystalline grooves which have been previously reported, they are both classified as similar type of nanovoids. Finally, twin lamellae as well as regular large twins were observed in the crystal. The twin lamellae correspond to shallow V-grooves revealed after the chemical etching.