Impact of Cu/III ratio on the near-surface defects in polycrystalline CuGaSe2 thin films
ABSTRACT Polycrystalline CuGaSe 2 thin films grown with various Cu/ III (= Cu / Ga ) ratios were investigated by positron annihilation spectroscopy (PAS). The line-shape parameter S of the spectra was used to characterize defects in CuGaSe 2 films. The S -parameter in positron annihilation spectra increased with decreasing bulk Cu/III ratio in the CuGaSe 2 film. Experimental results combined with theoretical calculation show the formation of multiple vacancy-type defect complexes in the near-surface region of the CuGaSe 2 film when Cu-content in the film is decreased. These point defects appear to cause the higher S -parameter in PAS measurement.