Zinc oxide, due to its specific is an important semiconductor material which already has many diverse applications. Undoped ZnO is usually n-type which is associated with presence of native point defects and/or residual hydrogen impurities. Fabrication of ZnO with p-type conductivity represented considerable challenge for many years. Recently, however, several groups achieved p-type ZnO by doping with group V elements. It has been shown that nitrogen has a simple substitutional character, while As and Sb form more complicated acceptor complexes .
Here we report on fabrication of p-ZnO layers doped with N and/or As and Sb acceptors by thermal oxidation of Zn based compounds (i. e., ZnTe, Zn3N2, Zn3Sb2). Optical study showed meaningful differences between samples doped with different acceptors.
Photoluminescence spectrum in the excitonic region shows three peaks in our samples: the peak located at 3.367 eV which we attribute to ionized-donor bound exciton, the peak at 3.361eV - to neutral donor bound exciton, and the peak located at 3.355 eV - to exciton bound to a neutral acceptor. We also observe additional peaks in ~3.3 eV region in some samples. The PL peak located at 3.311 eV is observed in samples doped only with N. It is worth to notice that the emission at this energy is absent in samples doped only with As. On the other hand, in ZnO:As and ZnO:Sb samples we observe emissions at 3.322 eV and 3.316eV, respectively. Therefore, we conclude that the 3.322 eV, 3.316 and 3.311 eV lines derive from excitons bound to the As, Sb and N acceptors, respectively. In nitrogen doped sample we observe also a peak, whose origin is not clear yet, located at 3.329 eV. Part of the research was supported by a Subsidy 8/2003 and grant 1P03B08430.
 S. Limpijumnong, S. B. Zhang, Su-Huai Wei, C. H. Park, Phys. Rev. Lett. 92, 155504 (2004).