High throughput Germanium Homoepitaxy using GeCl₄ in an APCVD Batch Reactor

To meet the rising demand for germanium, a critical raw material commonly used as substrates for highly efficient III-V solar cells, innovative, sustainable and cost-effective substrate alternatives, such as engineered germanium substrates and germanium on silicon virtual substrates, are currently under development. In this study, we developed a high throughput homoepitaxial germanium deposition process that can be applied to both substrate alternatives. We successfully deposited 10 µm thick, high-quality germanium epilayers at an elevated growth rate and high molar yield without compromising quality utilizing a batch-type atmospheric pressure chemical vapor deposition (APCVD) reactor in a GeCl4-H2 system. Under optimal deposition conditions at 750°C with a GeCl4/H2 ratio of 1.11 x 10-2, we achieved a significant growth rate of 0.37 µm/min and a molar yield of 36%. Characterization of the crystalline structure and surface morphology confirmed that the epilayers exhibit high crystalline quality, comparable to bulk Czochralski wafers, affirming their suitability as substrates for highly efficient III-V solar cells.