Low-temperature electron-paramagnetic-resonance study of extrinsic and intrinsic defects in CuGaSe2

The low-temperature electron-paramagnetic resonance (EPR) of the compound s emiconductor CuGaSe2 was investigated. Spectra of as-grown lumps and powder s with a defined maximum grain size were measured in X band. The spectra of two transition-metal impurities, Ni+ and Fe2+, could be identified and the ir appropriate EPR parameters an presented. The position of the Fermi-level energy within the forbidden zone as indicated by the occurrence of nickel and iron with these oxidation states is discussed by analogy with previous EPR investigations on other chalcopyrite semiconductors. An aging effect wa s observed, associated with the occurrence of EPR signals typical for Cu2+. The nature of the aging process is discussed with respect to the electroni c properties of CuGaSe2 for thin-film solar cell applications. [S0163-1829( 99)01019-X].