Effect of oxygen plasma-induced current blocking on the performance of GaN-based vertical light-emitting diodes

We investigated the effect of O₂ plasma-induced current blocking regions (O₂ -CBRs) on the performance of GaN-based vertical light-emitting diodes (VLEDs) as a function of the O₂ plasma rf power. The VLEDs fabricated with the O₂ -CBRs give forward voltages in the range 3.41-3.48 V at 350 mA, which are slightly higher than those in the case of VLEDs with and without SiO₂ current-blocking layers (CBLs). The output powers of VLEDs with O₂ -CBRs for rf powers of 50 and 100 W are 400.2 and 399.4 mW, respectively, which are slightly higher than those of the VLEDs with SiO₂ CBLs. Indium tin oxide (ITO)-based contacts to p-GaN show rectifying behaviors with Schottky barrier heights of 1.89 and 2.78 eV, when treated at rf powers of 50 and 100 W, respectively. X-ray photoemission spectroscopy (XPS) results show that for the samples treated at 50 W, the Ga 2p core level moves toward the higher binding-energy side as compared to that of the reference sample without plasma treatment. On the basis of the electrical characteristics and XPS results, we state that the O₂-CBR effect is due to the generation of donor-like defects at the p-GaN surface.