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

Abstract

Polycrystalline samples have been prepared of 12 defect chalcopyrite quaternary compounds of the form I III IV Se 4 , 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 (E g ) and all gaps shown to be direct. For the cases of AgGaSnSe 4 and AgGaGeSe 4 , values of E g 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 (E gT ) have been compared with those of the corresponding ternary chalcopyrite compounds (E gT ) and a relation between the values of E gQ −E gT and E gT shown.