$NiAi1.74Al0.26$ and $NiSi1.83Ga0.17:$ Two materials with perfect lattice match to Si

We report on the preparation and characterization of two materials based on cubic $NiSi2$ $(CaF2$-type, $cF12,$ $Fm3̄m)$ that show no lattice mismatch to Si and are thus promising materials for perfect epitaxial films grown on silicon. The perfectly lattice-matched materials are special compositions within the extended solid solution phases $NiSi2−xAlx$ and $NiSi2−xGax$ with $x=0.26$ for Al and $x=0.17$ for Ga, respectively. The variations of bulk lattice parameters with the composition were studied by means of x-ray diffraction and the melting behavior of the solid solution phases was investigated by differential thermal analysis. Both phases are thermally stable up to temperatures around $1000 °C.$ Phase diagram investigations show that the respective phases are in thermodynamic equilibrium with pure silicon. The electrical conductivity of $NiSi2−xAlx$ and $NiSi2−xGax$ was studied on selected bulk samples between 4.2 and 300 K. Both materials show metallic behavior with specific room-temperature resistivities between 23 and 40 μΩ cm. The difference is mainly due to intrinsic defects in these compounds.