One of the fundamental challenges for the realization of low-cost and high-efficiency multijunction solar cells is the integration of III-V with IV elements. Of particular interest is the monolithic integration of the ternary material SiGeSn with the InGaP/InGaAAs/Ge structure via Metal Organic Vapor Phase Epitaxy (MOVPE). This paper reports the new results relating to SiGeSn deposited by MOVPE in the same growth chamber used for III-V deposition. The ternary material was grown on 4- and 6-inch germanium wafers, without tin precipitation, at relatively high growth temperature (490°C), with Disilane, Tin Tetrachloride, and Germanum as gas precursors. The SiGeSn layers were characterized by high-resolution X-ray diffraction (HRXRD), scanning electron microscopy (SEM), secondary ion mass spectroscopy (SIMS), and electrochemical capacitance voltage (ECV) measurement. Functional InGaP(N)/SiGeSn(N)/Ge(P) heterojunction (HJ) devices were then fabricated and characterized by electroluminescence and IV measurements, at different solar concentrations. Under the AM1.5 G173 spectrum, considering a 400-nm thick GaAs filter, a short circuit current density of up to 18 mA/cm2 was measured with a Ta2O5/SiO2 coating. The EQE simulations of the experimental data allowed us to estimate an application of SiGeSn 22% higher than the current application that could provide Ge with the same thickness. To simulate absorption in a four-junction structure, a 2500-nm thick GaAs filter and a 1-eV energy gap SiGeSn layer were considered: a short-circuit current density of up to 16 mA/cm2 was obtained from filtered HJ. The measured and simulated current densities show the potential for successful integration of the grown SiGeSn MOVPE into the III-V MJ structure.