SPLTRAK Abstract Submission
GeCl4-based High Quality Ge epitaxy on Engineered Ge Substrates for Thin Multi-junction Solar Cells
Jinyoun CHO1, Clément Porret2, Valérie Depauw2, Guillaume Courtois1, Daniel McDermott2, Roger Loo2, Kristof Dessein1, Rufi Kurstjens1
1Umicore, Olen, Belgium
/2imec, Leuven, Belgium

Germanium, a critical raw material, is used as a template for III-V epitaxial growth and as a bottom cell in multi-junction solar cells. To reduce the amount of germanium used, a detachable substrate is very interesting, especially if the Ge foil thickness can be adjusted as needed. In this study, the potential of GeCl4-based epitaxy was demonstrated. A growth rate up to 190 nm/min and a thickness up to 15 µm were achieved. Detachable foils were then formed by porosification, annealing and epitaxial growth. The effective minority-carrier lifetime in the surface-passivated foil could be measured and proved quite high: over 25 µs. Therefore, it could be inferred that the seed layer had excellent surface properties for Ge epitaxy, and the germanium epitaxial layer grown thereon was of high quality.