The optoelectronic properties of multinary III-V semiconductors, their tunable band gap, reliable control of doping concentrations, and the formation of functional heterostructures such as tunnel junctions make them promising candidates for various high-performance device applications, e.g tandem photovoltaic devices, or photoelectrodes. Commonly, Ge (100) or GaAs(100) substrates, GaInP, and GaAs buffer layers play key roles in these architectures.