Improved ohmic contact of Ga-Doped ZnO to p-GaN by using copper sulfide intermediate layers

•Effect of copper sulfide (CuS) intermediate layers on the contact properties of GZO to p-GaN.•The contact mechanism analysis by XPS depth profile of p-GaN/CuS/GZO interfaces.•Effect of CuS intermediate layers on the performance of LEDs.•The epitaxy growth behavior of GZO films on CuS.

Copper sulfide (CuS) was used as the intermediate layer to build ohmic contact of Ga-Doped ZnO (GZO) transparent conduction layer (TCL) to p-GaN. The CuS and GZO layers were prepared by thermal evaporation and RF magnetron sputtering, respectively. Although the GZO-only contacts to p-GaN exhibit nonlinear behavior, ohmic contact with a specific contact resistance of 1.6 × 10−2 Ω cm2 has been realized by inserting 3 nm CuS layer between GZO and p-GaN. The optical transmittance of CuS/GZO film was measured to be higher than 80% in the range of 450–600 nm wavelength. The possible mechanism for the ohmic contact behavior can be attributed to the increased hole concentration of p-GaN surface induced by CuS films after annealing. The forward voltage of LEDs with CuS/GZO TCL has been reduced by 1.7 V at 20 mA and the output power has been increased by 29.6% at 100 mA compared with LEDs without CuS interlayer. These results indicated that using CuS intermediate layer could be a potential ohmic contact method to realize high-efficiency LEDs.

Graphical abstractCopper sulfide (CuS) was used as the intermediate layer to build ohmic contact of Ga-Doped ZnO (GZO) transparent conduction layer (TCL) to p-GaN.Figure optionsDownload full-size imageDownload as PowerPoint slide