Solar energy based on the solar cell is the most promising source among renewable energy sources. The photocurrent (Iph), open circuit voltage (Voc), maximum voltage (Vm), form factor (FF) and efficiency (η) of the solar cell are the most important parameters that can define the quality of this cell. In this work, we study the impact of the junction depth Xj and the surface recombination velocity Sn on these parameters in both external and internal cases of the solar cell in Arsenic gallium (GaAs) technology using the MATLAB software as a tool. Results show that in order to obtain high-performance of GaAs-solar cells must be the surface recombination velocity value is low, and the junction depth in submicron scale. Numerical results gave higher values of efficiencies 19.21 % and 30.1 % in external and internal cases respectively, and best electrical parameters of the GaAs-solar cell when the junction depth and the surface recombination velocity are equal to 0.2 μm and 102 cm/s respectively.