The wider-gap members of a semiconductor series such as or often cannot be doped -type at equilibrium. We study theoretically if this is the case in the chalcopyrite family , finding that: (i) Bulk (CIS, ) can be doped at equilibrium -type either by Cd or Cl, but bulk (CGS, ) cannot; (ii) result (i) is primarily because the Cu-vacancy pins the Fermi level in CGS farther below the conduction band minimum than it does in CIS, as explained by the “doping limit rule;” (iii) Cd doping is better than Cl doping, in that yields in CIS a higher net donor concentration than ; and (iv) in general, the system shows massive compensation of acceptors and donors .
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In case of Cd-doping of CIS, using a Cd chemical potential corresponding to equilibrium with CdSe results in undesirably high Cd incorporation. Therefore, we used here a slightly lower (by 0.2 eV).
