The role of deep donor-deep acceptor complexes in CIS-related compounds

Deep PL emission bands are observed in several samples of CuGaSe2. CuIn0.5Ga0.5Se2 and CuInS2. In all these materials these bands have a closely similar structure. The D1 and D2 bands centered at hv = 1.148 and 1.042 eV in CuGaSe2 at hv = 0.948 and 0.857 eV in CuIn0.5Ga0.5Se2 and at hv(= 0.954 eV and 0.864 eV in CuInS2, respectively, are concluded to result from a donor-acceptor pair (DAP) recombination. inch that the donor atom of the DAP occupies an interstitial position within the chalcopyrite lattice and rhc acceptor atom resides at a cation site (either In or Ga) next to it. The probable donor defect is identified as an interstitial Cu atom and the associated acceptor defect as a cation vacancy, i.e. either V-In or V-Ga. On the basis of the simple Coulombic interaction Z(A)Z(D)e(2)/(epsilon r) between the components of the DAP, additional deep bands D3, D4, D5,...,are predicted. In the present work we find these additional emissions experimentally in CuInS2 and CuIn0.5Ga0.5Se2, but not in our CuGaSe2 samples. (C) 2000 Elsevier Science S.A. All rights reserved.