Nature of semiconductor-to-metal transition and volume properties of bulk tetrahedral amorphous GaSb and GaSb-Ge semiconductors under high pressure.

Electrical properties and compressibility of bulk amorphous semiconductors $a\ensuremath{-}{(\mathrm{GaSb})}_{1\ensuremath{-}x}{({\mathrm{Ge}}_{2})}_{x}(x=0 \mathrm{and} 0.27)$ were investigated at high pressure. Discontinuous crystallization of $a\ensuremath{-}{(\mathrm{GaSb})}_{0.73}{({\mathrm{Ge}}_{2})}_{0.27}$ occurs at 4.7 GPa. In $a\ensuremath{-}(\mathrm{GaSb})$ the continuous volume anomaly occurs at 3-7 GPa, whereas the semiconductor-to-metal transition occurs at 3-4 GPa. Metallization of $a\ensuremath{-}(\mathrm{GaSb})$ occurs by the percolation mechanism involving interaction of nanoregions with higher coordination. Bulk moduli of amorphous compounds at normal pressure are less (35 and 40 GPa for $x=0 \mathrm{and} 0.27$, respectively) than that of crystalline (GaSb) (55 GPa) and exhibit strong softening long before the transitions.