Abstract: A vacuum chamber is provided for sputter deposition of a semiconductor homojunction. A target made of a semiconductor compound containing at least one non-metallic element is provided. A substrate for receiving the sputtered species from the target to form sequential layers of deposited semiconductor material is also provided. An electric field is provided between the target and the substrate. An inert gas is introduced sequentially at a plurality of discrete partial pressures to adjust the incident energy of the sputtered species by thermalization, for altering the mean free path of the sputtered and incident species to control the ratio of non-metallic to metallic elements in the deposited semiconductor material and create a plurality of different semiconductor material layers.