P-Type ZnO as Multifunctional Material for Optoelectronic Devices

ZnO is one of the most important members of transparent conductive oxide (TCO) materials. ZnO forms a technologically important class of material, exhibiting exceptional UV attenuation characteristics, blocking 95% of all UV radiation.Since the bandgap of ZnO is well above the visible region, prepared film are electrically conductive, which is leading to application for transparent p-n junction devices. ZnO naturally shows n-type conductivity due to a large number of native defects, such as oxygen vacancies and zinc interstitials, which leads to difficulty in achieving p- type ZnO thin films. The difficulty in the formation of p-type ZnO material is due to its self compensation effect, deep accepter level and low solubility of accepter dopants. Generally, realization of ZnO thin film p-type conductivity may be possible by substituting group-I elements (Li, Na, K and Ag) for Zn sites, or group-V elements (N, P, As, Sb) for O sites, or substituting group-III and V elements simultaneously for Zn and O sites respectively.