Characteristics of p-ZnO/n-GaN heterojunction photodetector

Thin film heterojuction of the type p-ZnO/n-GaN was prepared by spray pyrolysis and electron beam evaporation technique, respectively. Hall measurements demonstrate the firm p-type conductivity of the p-doped ZnO film. The structural and electrical properties of the p-ZnO/n-GaN heterojunction are investigated by X-ray diffraction (XRD) and current-voltage (I-V) measurements. The XRD shows that the p-ZnO/n-GaN heterojunction is highly crystalline in nature with preferred orientation along the [0001] direction. The current-voltage curve of the heterojunction demonstrates obvious rectifying diode behavior in the dark and under illumination conditions. The ideality factor of the detector was determined in case of forward bias at low voltages and it was found to be 13.35. The turn-on voltage appears at about 1V under forward-biased voltage, and the reverse breakdown voltage is about 4V. It was found that the current of the illumination increases with the increase of bias voltages.