In order to take steps towards the monolithic integration of III-V and IV compounds in multijunction solar cells, a first evaluation of SiGeSn deposition was carried out in a MOVPE deposition chamber also used for the deposition of III-V. The study offers insights into different aspects of MOVPE SiGeSn growth in order to achieve better control of ternary composition and morphology. In particular, the study demonstrates that the Si2H6 gas source is more influenced by the growth temperature than the precursors GeH4 and SnCl4; furthermore, there is a competition between Si2H6 and SnCl4, which makes it difficult to incorporate Si into SiGeSn, as the partial pressure of SnCl4 increases. The morphology of SiGeSn is strongly dependent on temperature, As carry-over effect and growth rate. A new growth model is proposed to explain the importance of bond lengths of adsorbed atoms in inhibiting tin segregation when SiGeSn is deposited at relatively high growth temperatures (>480 °C). In order to investigate the photovoltaic behavior of SiGeSn, a functional single-junction GaAs/InGaP/SiGeSn/Ge device was produced and characterized with external quantum efficiency (EQE) and current-voltage measurements. The measurement of EQE and the simulation of experimental data show that the absorption coefficient of SiGeSn is greater than that of Ge; this allows us to use SiGeSn layers of one third of the thickness needed if Ge were used to produce the same photovoltaic current.