Quaternary Defect Chalcopyrite Compounds I III IV VI4

Abstract

The crystallographic and optical properties determined for twelve compounds of the form I III IV □Se4 are reviewed, the compounds being those formed by combinations of the elements I Cu, Ag: III Al, Ga, In: IV Ge, Sn. It is found that all of the compounds have the chalcopyrite structure and lattice parameter values have been determined for each. These values are compared with those of the corresponding ternary chalcopyrite I III Se2 compounds and a systematic variation between the parameters for ternary and quaternary compounds is shown. Energy gap values have been determined for the twelve compounds by optical absorption measurements. These also have been compared with the values for the corresponding ternary compounds and again a systematic variation shown. Finally, reflectance spectra have been determined as a function of temperature for a single crystal sample of CuGaSn □Se4 and hence the temperature variation of the three valence band-conduction band gaps investigated.