In the H2Demo project, processes to produce economical III-V-Si tandem structures and the necessary plant technology are being developed. In work package 2, the focus is on the development of high-throughput epitaxy processes, which should contribute to a significant cost reduction in the future. This will first be implemented for GaAs single-junction solar cells, which are epitaxied at growth rates > 60 µm per hour in a few minutes. Based on this, the innovative epitaxy processes will be optimised for the target device of a GaAsP/Si tandem solar cell grown directly on Si. Finally, an industrial evaluation will be carried out with the aim of industrialising these processes and to gain a precise understanding of the cost advantages generated.