A Schottky ultraviolet photodiode using a (0001) ZnO single crystal grown by the hydrothermal growth method is reported. The photodiode consisted of a semitransparent Pt film for the Schottky electrode and an Al thin film for the Ohmic electrode. The photodiode had polarity dependences on current-voltage characteristics and on responsivity. In the case of the Schottky electrode on the zinc surface, the responsivity was 0.185A∕W at a wavelength of 365nm. On the other hand, the responsivity was 0.09A∕W for an oxygen surface. The results are attributed to the polarity dependences of surface chemical reactivity and the surface state density on ZnO surfaces.

We report on the effect of sample non-uniformity on the results of Hall-effect measurements. False positive Hall coefficients were obtained from an evidently n-type ZnO single crystal, although four electrodes with low contact resistance were made and the Van der Pauw parameter for this electrode configuration was close to 1.00. Further position-sensitive characterization revealed that the false positive Hall coefficient was due to non-uniform electrical properties of the sample. To demonstrate a false positive sign of the Hall coefficient due to sample non-uniformity, we devised a model structure made from evident n-type ZnO thin film and successfully reproduced a false positive Hall coefficient from n-type ZnO.

No abstract

No abstract

No abstract