The results of simulations and analyzes that have been carried out using Archimedes 2.0.1 are compared to the results of experiments that have been published. The characteristic is a current-voltage graph at p+-Si/n+-GaAs heterojunction. The comparison shows very good accuracy, 99.99%. The purpose of our study is to determine and explain the distribution of electrons in the depletion region, and their effects on the bias voltage applied to p+-Si/n+-GaAs heterojunction. From the simulation and analysis results obtained the depletion region is indicated at around the point 515 to 520 μm. Also, there is an influence on the bias voltage applied to p+-Si/n+-GaAs heterojunction, which is indicated by increasing the electron density value in the depletion region, because there are more electrons flowing in the device.