Identification of the isolated deep Ni acceptor in CdTe and ZnTe: comparison with isomorphous systems

Abstract
Single crystals of CdTe and ZnTe doped with nickel have been investigated by electron spin resonance. Among other signals they exhibit an isotropic line near mod g mod =1.4 which is identified as being due to the isolated, ionised Ni acceptor state, NiCd+(3d9) and NiZn+(3d9). Central hyperfine interaction with 61Ni and ligand hyperfine interaction with 125Te could be resolved for CdTe:Ni. Intra d-shell optical transitions of Ni+ in CdTe were also observed. The general properties of the Ni(d8/d9) acceptor in cubic IIB-VI and III-V compounds are pointed out and are contrasted with those of the copper acceptor in IIB-VI compounds. A tentative prediction for the Ni acceptor level in CdTe is made.