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

The low-temperature electron-paramagnetic resonance (EPR) of the compound semiconductor CuGaSe2 was investigated. Spectra of as-grown lumps and powders 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 their 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 was observed, associated with the occurrence of EPR signals typical for Cu2+. The nature of the aging process is discussed with respect to the electronic properties of CuGaSe2 for thin-film solar cell applications. [S0163-1829(99)01019-X].