Effects of metalorganic chemical vapor deposition growth conditions on the GaAs/Ge solar cell properties

We have studied the effects of metalorganic chemical vapor deposition (MOCVD) growth conditions on the properties of GaAs solar cells grown upon Ge substrates, and in particular the GaAs/Ge interface. The interface properties were found to strongly depend on growth conditions. By small changes in the growth temperature, the GaAs/Ge interface was altered from active to passive. Only a narrow temperature window (600–630 °C) for the initial GaAs layer growth gave the passive‐Ge junction together with good surface morphology. Accordingly, a high efficiency (19%, AM0) GaAs solar cell was grown by atmospheric pressure MOCVD on a Ge substrate without any junction in the Ge.