Manufacturing process for III–V multijunction solar cells on germanium substrates with a total thickness below 60 microns

In this work, we demonstrate a new manufacturing process that allows to fabricate thin solar cells avoiding problems related to the brittleness or fragility of thin wafers without needing any carrier nor temporary substrate. This technique has been successfully applied to Ge single and GaInP/Ga(In)As/Ge triple‐junction solar cells grown on Ge substrates, achieving 47.5‐ and 55.5‐μm‐thick substrates, respectively. Although this technique should allow to thin substrates to any desired thickness, a final thickness around 20–30 μm is recommended due to practical concerns such as the uneven substrate thickness throughout the wafer. In any case, a III–V solar cell with such a thickness should be thin enough for most applications and, in particular, for space ones. A new manufacturing process to thin down Ge‐based solar cells below 60 µm without any temporary substrate was demonstrated. Weight is decreased by more than 65%, while 50% of the free carrier absorption is avoided. The process was successfully applied to 4″ wafers.