Since ZnO is a wide band gap (3.37 eV) semiconductor with a large exitonic binding energy (60 meV), it has been considered as a candidate for various applications, such as ultraviolet (UV) light emitting diodes and laser diodes. For the applications of ZnO-based optoelectronic devices, it is necessary to produce n and p type ZnO films with the high quality. Since ZnO is naturally n-type semiconductor material due to intrinsic defects, such as oxygen vacancies, zinc interstitials, etc., it is easy to produce n-type ZnO with high quality. However, it is difficult to produce low-resistive and stable p-type ZnO due to its asymmetric doping limitations and the self-compensation effects of the intrinsic defects. According to the theoretical studies, p-type ZnO can be realized using group-V dopants substituting for O, such as N, P and As. Among them, N has been suggested to be an effective acceptor dopant candidate to achieve p-type ZnO, because that nitrogen has a much smaller ionic size than P and As and the energy level of substitutional NOis lower than that of substitutional POand AsO.Transparent p-type ZnO: N thin films have been fabricated using the pulsed laser deposition method at deposition temperatures 800 °C under the O2and N2mixing pressure 6Pa. N-doped ZnO films were deposited on sapphire substrate using metallic zinc (99.999%) as target. The structural, optical and electrical properties of the films were examined by XRD, UV-visit spectra and Hall effect measurement. We found that thin film contain the hexagonal ZnO structure. The Hall effect measurement revealed that the carrier concentration is 5.84×10181/ cm3, and Hall mobility is 0.26 cm2/Vs, electrical resistivity is 4.12ohm-cm. Film thickness is 180nm. Besides, Visible light transmittance is more than 80%, and calculative band-gap is 3.1 eV, which is lower than ZnO.
Ag doped p-type ZnO films and its optical and electrical properties