Energy gap values by optical absorption in I III IV Se4 compounds

Polycrystalline samples have been prepared of 12 defect chalcopyrite quaternary compounds of the form I III IV Se4, where I is Cu or Ag, III Al, Ga or In, and IV Ge or Sn. In all cases room temperature optical absorption measurements have been made to determine values of the fundamental energy gap (Eg) and all gaps shown to be direct. For the cases of AgGaSnSe4 and AgGaGeSe4, values of Eg have been determined as a function of temperature from helium to room and the data fitted to a Manoogian–Leclerc equation. The energy gap values of the quaternary compounds (EgT) have been compared with those of the corresponding ternary chalcopyrite compounds (EgT) and a relation between the values of EgQ−EgT and EgT shown.