CHARACTERIZATION OF QUATERNARY CUGA1-XINXTE2 THIN-FILMS DEPOSITED BY THERMAL EVAPORATION

Structural, electrical and optical properties of thin films of the Cu-In-Ga-Te system grown by thermal evaporation have been studied relating the measured film composition to these properties. Above a substrate temperature of 250 degrees C the chalcopyrite structure is obtained and films deficient in Te by up to 16% show this structure. The optical absorption coefficients of the films present two or three inflection regions corresponding to several energy gaps, two direct and one forbidden direct gap. The first direct gaps lie between 0.46 and 0.88 eV and the second ones in the 1.01-1.37 eV range. The forbidden direct gaps are in the 0.94-1.83 eV range. The first gap appears only in the samples with Cu/In > 1.06. The values of the second energy gap and the cell parameters of tetragonal phase depend on composition, i.e. on Cu/Ga atomic ratios. The measured resistivities and mobilities of samples are ranged in the 0.001-1.63 Omega cm and 5-38 cm(2) V-1 s(-1) ranges respectively. The samples were p-type or n-type; those with a defect in Te were n-type. Thermal treatments have been done in a hydrogen flux at 350 degrees C. This annealing varies notably the initial number of phases of the films notably.