Nitrogen and aluminum codoped p-type ZnO films and ZnO p–n homojunctions

The most significant impediment to the widespread exploitation of ZnO-related materials in electronic and photonic applications is the difficulty in p-type doping and synthesizing ZnO p–n homojunctions. To resolve the problem of p-type doping in ZnO, nitrogen and aluminum (N–Al) codoped ZnO films were prepared by ultrasonic spray pyrolysis technique. The structural, optical and electrical properties of the as-grown ZnO films were investigated by X-ray diffraction (XRD), photoluminescence (PL) spectra, Hall-effect and Seebeck-effect measurements. The results demonstrate that the N–Al codoped ZnO films show extremely excellent p-type conduction and good ultraviolet emission characteristics. Furthermore, ZnO homojunctions were synthesized by depositing the undoped ZnO layers on the N–Al codoped ZnO layers, and the current–voltage (I–V) characteristics measured from the two-layer structure show a typical rectifying characteristics of p–n junctions with a low turn-on voltage of about 2.5 V.