Influence of Germanium Content on the Properties of Cu₂Zn(SnGe)Se₄ Thin Films Deposited by Sequential Thermal Evaporation Technique Studied by Photoacoustic Technique

Herein, the influence of the germanium (Ge) content on the surface recombination velocity, nonradiative carrier recombination time, and thermal diffusivity of Cu₂Zn(SnGe)Se₄ compound from photoacoustic (PA) measurements is presented. The compounds are synthesized by a sequential thermal evaporation technique and thermal annealing. The order of the metallic stacks deposited on the coated molybdenum glass substrates is Cu/Sn/Cu/Zn/Ge. The thicknesses of Cu(3 nm)/Sn(248 nm)/Cu(112 nm)/Zn (174 nm) are kept constant, and only the thickness of the Ge layer is varied between 10 and 30 nm. The incorporation of germanium shows changes in the aforementioned parameters in dependence of the Ge content. Atomic force microscopy (AFM) as complementary measurements to the PA is carried out. The results are presented and discussed in terms of the influence of Ge content on the properties of the copper zinc tin germanium selenium (CZTGSe) compounds.