Effects of Hydrogen Plasma Treatment on the Electrical and Optical Properties of ZnO Films:Identification of Hydrogen Donors in ZnO

摘要

Wurtzile ZnO has many potential applications in optoelectronic devices, and the hydrogenated ZnO exhibits excellent photoelectronic properties compared to undoped ZnO. however, the structure of H-related defects is still unclear. In this article, the effects of hydrogen-plasma treatment and subsequent annealing on the electrical and optical properties of ZnO films were investigated by a combination of Hall measurement, Raman scattering, and photoluminescence. It is found that two types of hydrogen-related defects, namely, the interstitial hydrogen located at the bond-centered (H_(BC)) and the hydrogen trapped at a O vacancy (Ho), are responsible for the n-type background conductivity of ZnO films. Besides introducing two hydrogen-related donor stales, the incorporated hydrogen passivates defects at grain boundaries. With increasing annealing temperatures, the unstable H_(BC) atoms gradually diffuse out of the ZnO films and part of them are converted into Ho. which gives rise to two anomalous Raman peaks at 275 and 510 cm~(-1) These results help to clarify the relationship between the hydrogen-related defects in ZnO described in various studies and the free carriers thai are produced by the introduction of hydrogen.