Composition dependence of viscosity for molten Ga_1-xAs _x (0.0≤x≤0.53)

Viscosity of molten Ga_1-xAs_x was directly measured by an oscillating cup method. The composition dependence of the synergism viscosity remarkably increases in the vicinity of stoichiometric composition; strong temperature dependence of viscosity was also observed at that composition. Activation energy for viscous flow at the stoichiometric Ga _1-xAs_x (x=0.5) melt ranges from 250 to 600 meV, which was larger than those of metals such as gallium and indium whose activation energies were about 60-100 meV. We estimate, therefore, that the melt of stoichiometric composition has middle-range ordering like an aggregation whose range is larger than that of short-range ordering in metals such as gallium and indium.