Germanium as an Enabler for Large Volume Production in PV and Photonics

The rapid evolution of the space industry, driven by reduced costs to orbit and increased launch availability, has catalyzed unprecedented growth in the space sector and a surge of new startups. All space applications require reliable power sources, contributing to the expansion of the photovoltaic (PV) segment. Conventional space-grade multi-junction solar cells utilize a dual-junction MOCVD-grown GaAs epi-stack on a germanium (Ge) substrate, with lithography/PVD-based interconnections. To enable the anticipated 10-fold increase in production scale over the next decade, a fundamental transformation of these three key components - MOCVD growth, Ge substrates and metallization - is essential. Geopolitical factors have further complicated this landscape. Recent export restrictions imposed by the Chinese government have led to a more than twofold increase in the price of Ge raw materials. This work presents a solution that addresses these economic and material challenges by enabling the reuse of Germanium substrates. This approach lowers the cost of ownership and unlocks much greater potential for high-volume production of III-V solar cells on Ge substrates. In parallel, the growing consumer market is driving rapid advancements in photonic devices, such as micro-LEDs, long-wavelength Vertical-Cavity Surface-Emitting Lasers (VCSELs), and imagers operating in the Near-Infrared (NIR) and Short-Wave Infrared (SWIR) spectrums. While Gallium Arsenide (GaAs) substrates dominate current photonics device manufacturing, emerging research highlights the advantages of Germanium over GaAs. Photonic device manufacturing is traditionally the domain of III-V integrated device manufacturers (IDMs) and foundries. However, the development of cutting-edge photonic chips requires close collaboration between III-V companies and Silicon semiconductor/CMOS players to improve form factors, enhance device performance, and reduce production costs. This integration is currently constrained by the limited wafer size of GaAs and the contamination requirements of CMOS fabrication. Umicore addresses these challenges by developing 8” and 12” Ge substrates that bridge the gap between the III-V and semiconductor industries. Germanium’s compatibility with CMOS specifications and the larger wafer sizes facilitate integration with existing semiconductor processes. Additionally, substrate reuse technology supports high-volume photonics applications compatible with CMOS, positioning Ge as a critical enabler in both PV and photonics industries.