Solid-state reactions of nickel thin films with GaAs: A comprehensive analysis

The development of CMOS-compatible contacts for III-V materials, particularly GaAs, is essential for various microelectronic and optoelectronic applications. This study presents a detailed analysis of the solid-state reaction between a Ni thin film and GaAs layers. The phase formation sequence was investigated using a range of X-ray diffraction and electron microscopy techniques. At lower temperatures, Ni is gradually consumed, resulting in the formation of the ternary Ni3GaAs phase between 250 and 300 degrees C. However, this Ni3GaAs phase is thermally unstable; its stoichiometry changes with increasing temperature, and it decomposes into two binary phases, NiAs and gamma-Ni3Ga2, between 450 and 500 degrees C. All intermetallic phases formed within the Ni/GaAs system exhibit the B8 hexagonal crystal structure and share a consistent orientation relationship with the GaAs substrate: Ni/GaAs intermetallic <1 1 0> (1 0 1)// GaAs <1 1 0> (0 0 1). This orientation relationship is identified in both ternary and binary phases and remains consistent throughout the phase sequence.