The ion implantation is well-established techniques for device fabrication in III-V semiconductors. GaAs is grown on Silicon (Si) substrate using Germanium (Ge) as a buffer layer to reduce the lattice mismatch. The implantation of nitrogen ions in GaAs layers of the epitaxial-grown structure GaAs/Ge/Si is done with sequential implantation of doses from 0.8 x 1017 to 2.0 x 1017 cm-2 with respective energies ranging from 40 keV to 120 keV per atomic ion. This was aimed to achieve more uniform depth distribution of nitrogen as a result of multiple ion implantation. A subsequent high temperature annealing is done for nanostructures formation and to improve the crystal quality. For the annealing process, rapid thermal annealing (RTA) and furnace annealing (FA) are used in temperature range of 700°C-850°C under argon and nitrogen environment. Current-voltage (I-V) characterization are carried out to study the effect of the post-annealing process on the barrier height and ideality factor. The electrical parameters are observed to have a strong dependence on temperature. The inhomogeneity in barrier height gives rise to the temperature dependence of barrier height. © 2019 Indian National Science Academy. All rights reserved.