AuGe‐Ni is widely used for the fabrication of ohmic contacts ton‐GaAs. The alloying behavior of evaporated AuGe‐Ni alloyed by furnace and scanning electron beam (SEB) is characterized by Rutherford backscattering with 2‐MeV4He+ions. The redistribution and diffusion of constitutents involved in the ohmic contact formation is studied by comparing the experimental spectrum with theoretically computed spectra. The studies show that SEB‐alloyed contacts undergo less redistribution of contact constituents compared with furnace‐alloyed contacts. It is established that the penetration depth of Au for furnace‐alloyed contacts increases with metallization thickness, whereas for SEB‐alloyed contacts the penetration depth is independent of metallization thickness.