EFFECTS OF COMPOSITION AND SUBSTRATE TEMPERATURE ON THE ELECTRO-OPTICAL PROPERTIES OF THIN-FILM CuInSe2 AND CuGaSe2.

Polycrystalline thin films of CuInSe//2 and CuGaSe//2 deposited by thermal evaporation onto heated substrates of 7059 glass and Al//2O//3 were studied. The data for CuInSe//2 indicates an absorption coefficient as high as 1. 5 multiplied by 10**5 cm** minus **1, though predominantly (2. 0-8. 0) multiplied by 10**4 cm** minus **1, and band-gap values ranging from 0. 94 to 1. 02 eV, with band-gap narrowing observed for films deposited at 350 degree C. The effect of high temperatures and lower copper concentrations in CuInSe//2 and CuGaSe//2 is to shift the onset of absorption to higher energies. The data for CuGaSe//2 thin films indicate absorption coefficients up to (1-2) multiplied by 10**5 cm** minus **1 at 500 nm and band gaps ranging from 1. 66 to 1. 72 eV. The effect of higher substrate temperatures on CuGaSe//2 is to eliminate secondary phases and minimize residual absorption below the band gap. The electrical measurements on CuInSe//2 indicate activated conductivity and show the films to be highly compensated by donors and acceptors whose origins are the native defects arising from non-stoichiometry.