Application of Ar⁺ion implantation for obtaining nanocontacts on the GaP (111) single crystals surface

Ultrathin ohmic contacts were fabricated on GaP(111) single crystals using argon ion (Ar⁺) implantation at an energy of E₀ = 2 keV and a dose of D = 2 × 10¹⁷ cm⁻², under high vacuum conditions (10⁻⁷ Pa). Post-irradiation analysis revealed a significant enrichment of the surface with gallium, reaching a concentration of approximately 90 at.%. Subsequently, a nickel (Ni) film with a thickness of about 1000 Å was deposited onto the GaP(111) surface to form the contact. This metallization step led to a three- to fourfold reduction in the total thickness of the contact layer compared to conventional approaches. Upon thermal treatment at T = 850 K, the initially disordered GaP(111) layers recrystallized, resulting in a polycrystalline contact structure. After annealing, the thickness of the contact layer increased by approximately 1.5 times, reaching 400–450 Å, which is still around 2.5 times thinner than the characteristic thickness (dₙ) in the Ni/pure-GaP system. These findings demonstrate that ion implantation, followed by controlled metallization and annealing, provides an effective route for producing ultrathin, thermally stable ohmic contacts for GaP-based semiconductor devices.