Has substitutional nickel two acceptor- and one donor-level in Si?

In the present study we question the origin of three dominant DLTS peaks observed in Ni-doped n- and p-type Si. Previously, these peaks with the activation energies of Ec−0.08 eV (E45), Ec−0.4 eV (E230) and Ev+0.17 eV (H80) were assigned to the double acceptor, single acceptor and single donor states of substitutional Ni. However, the concentration of E45 was measured in our samples to be about three times smaller than that of E230. The absence of the enhancement of the emission rate of E45 with electric field is also not consistent with the assignment of this defect to the double acceptor state of Nis where the lowering of the potential barrier should be observed under the electric field applied to the diode. In addition, we will show that the annealing temperatures of the Ni defects differ significantly in n- and p-type silicon. The origin of these defects will be discussed.