We report the characterization of ZnO homojunction fabricated with undoped ( n-ZnO) and AlN codoped ZnO ( p-ZnO) films by RF magnetron sputtering. We directly doped (codoped) AlN into ZnO to obtain p-ZnO instead of conventional codoping method. The Current-Voltage characteristics of the fabricated p-n junction show a typical rectification behavior. The junction parameters such as ideality factor (11.85), barrier height (0.782 eV) and series resistance (33 kΩ) have been determined using Cheung’s method. The barrier height (0.805 eV) determined by Norde’s method is also in good agreement with Cheung’s method. ► In this paper, we discussed about the characterization of p- n junction fabricated with undoped ZnO ( n-type) and AlN codoped ZnO ( p-type) ► The fabricated junction on Si (100) by RF magnetron sputtering has been subjected to XRD, AFM, EDS, PL, Hall measurements and I-V characterization ► It has been demonstrated that the fabricated ZnO homojunction is suitable for optoelectronic and gas sensor devices