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

Deep PL emission bands are observed in several samples of CuGaSe2. CuIn0.5G a0.5Se2 and CuInS2. In all these materials these bands have a closely simil ar structure. The D1 and D2 bands centered at hv = 1.148 and 1.042 eV in Cu GaSe2 at hv = 0.948 and 0.857 eV in CuIn0.5Ga0.5Se2 and at hv(= 0.954 eV an d 0.864 eV in CuInS2, respectively, are concluded to result from a donor-ac ceptor pair (DAP) recombination. inch that the donor atom of the DAP occupi es an interstitial position within the chalcopyrite lattice and rhc accepto r 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 ac ceptor defect as a cation vacancy, i.e. either V-In or V-Ga. On the basis o f the simple Coulombic interaction Z(A)Z(D)e(2)/(epsilon r) between the com ponents of the DAP, additional deep bands D3, D4, D5,...,are predicted. In the present work we find these additional emissions experimentally in CuInS 2 and CuIn0.5Ga0.5Se2, but not in our CuGaSe2 samples. (C) 2000 Elsevier Sc ience S.A. All rights reserved.