The performance of GaInP/GaAs tandem solar cells with AlInP growth temperatures of 680$^{circ}C$ and 700 $^{circ}C$ on n-type GaAs (100) substrate with 2$^{circ}$ and 6$^{circ}$ tilt angles has been investigated. The series resistance and open circuit voltage of the fabricated tandem solar cells are affected by the substrate tilt angles and the growth temperatures of the window layer when zinc is doped in the tunnel diode. With carbon doping as a p-type doping source in the tunnel diode and the effort of current matching between top and bottom cells, GaInP/GaAs tandem solar cell has been exhibited 25.58% efficiency.