Polarity Determination of Polarity-Controlled ZnO Films Using Photoresponse Characteristics

Abstract

We report on the use of the photoresponse characteristics of polarity- controlled ZnO films for determining ZnO polarity. ZnO films were grown on CrN and Cr2O3 buffer layers in order to produce Zn- and O-polar films, respectively, and Ti/Au metal contacts were formed. All samples showed Ohmic behavior, but the Zn-polar ZnO film showed lower contact resistance than the O-polar ZnO film. The O-polar ZnO film showed higher photocurrent and longer decay time than the Zn-polar film by photoresponse measurement. These phenomena can be explained by the expansion of the depletion layer into the bulk ZnO surface. Compared with current methods, this method of determination of the polarity of ZnO films through the measurement of photoresponse characteristics is very easy and simple to implement.