A method is disclosed for passivating and contacting a surface of a germanium substrate. A passivation layer of amorphous silicon material is formed on the germanium surface. A contact layer of metal, e.g., aluminum, is then formed on the passivation layer. The structure is heated so that the germanium surface makes contact with the contact layer. The aluminum contact layer can be configured for use as a mirroring surface for the back surface of the device. Thus, a passivated germanium surface is disclosed, as well as a solar cell comprising such a structure.