Nitrogen-doped ZnSe layers have been grown using dimethylzinc and H2Se as precursors and N2 or N2+3H2 plasma as a dopant. With decreasing the VI/II flow ratio, N acceptors are incorporated more effectively. In the case of N2 plasma doping, the intensity of N acceptor-bound exciton emission is much higher than that of donor-bound exciton emission, but the layers exhibit n-type conductivity and the free-electron concentration increases with decreasing the VI/ II ratio. In the case of N2+3H2 plasma doping, on the other hand, the layers exhibit high resistivity and, after subsequent rapid thermal annealing at 700°C, some layers show p-type conductivity with hole concentration of∼1×1015 cm-3. This indicates that hydrogen causes not only passivation of the N acceptors but also suppression of the generation of donors. Methyl radicals play an important role in producing donor species. Prior to plasma doping, it is needed to prepare Zn-rich surface without methyl radicals in order to obtain p-type N-doped ZnSe layers.
An electrodeposited Zn-Ni alloy coating (Ni 15.3 at.%) has been investigated by ultraviolet and x-ray photoelectron spectroscopies in order to elucidate the electronic structure. The Ni 3d band of the alloy coating has 1-eV-higher binding energy and narrower width compared with that in Ni metal. The Ni 2p main line in the alloy coating is also narrower and less asymmetric. The Ni 2p two-hole satellite in the alloy coating locates at 7.5 eV below the main line and is weak in relative intensity. These results suggest that the Ni 3d band is filled by a charge transfer from Zn and pulled down below the Fermi level, leading to low density of states of the band at the Fermi level. It is also found that a 9-eV-energy-loss peak of Zn is weaker in the alloy coating than Zn metal.