Influence of growth temperature and post-annealing on an n-ZnO/p-GaN heterojunction diode

•n-ZnO grown on p-GaN with growth temperatures (450–600 °C) by RF Sputtering.•c-axis orientation (002) regardless of growth temperature. PL showed a dominant NBE emission.•The turn-on voltage of the diode:- 3.2 V for the annealed films produced at 500 °C.•The small amount of leakage current was observed to be ∼10−4 mA.•The ideality factor of annealed samples, n, 1.45 at 450 °C, and 1.37 at 500 °C.

We report on an n-ZnO/p-GaN heterojunction diode fabricated from zinc oxide (ZnO) films at various growth temperatures (450, 500, 550, and 600 °C) by RF sputtering. The films were subsequently annealed at 700 °C in N2 ambient. To investigate the influence of the growth temperature of n-ZnO films, the microstructural, optical, and electrical properties were measured using scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), and Hall measurements. The XRD pattern showed the preferred orientation along the c-axis (002) regardless of growth temperature. The PL spectra showed a dominant sharp near-band-edge (NBE) emission. Current–voltage (I–V) curves showed excellent rectification behavior. The turn-on voltage of the diode was observed to be 3.2 V for the films produced at 500 °C. The ideality factor of ZnO film was observed to be 1.37, which showed the best performance of the diode.