Ga homogenization by simultaneous H2Se/H2S reaction of Cu-Ga–In precursor

The compositional distribution of Ga and S in Cu(InGa)(SeS)2 films fabricated by a simultaneous selenization and sulfization process was systematically investigated. At low H2Se/H2S reaction temperature (490 °C), most Ga remains at the back of the film adjacent to the Mo back contact. However, the Ga/III ratios at the top and bottom of the Cu(InGa)(SeS)2 layer monotonically increase and decrease with reaction temperatures, respectively. At T>550 °C, homogeneous distribution of elemental Ga and In through film is achieved. Further increase of the reaction temperature (e.g., T>550 °C) causes phase segregation on the surface of the Cu(InGa)(SeS)2 film confirmed by XRD, GIXRD and EDS analysis.