Analyses of laser-induced p-type doping of GaN in the improvement of light-emitting diodes

We increase the hole concentration of the p-GaN contact layer of the epitaxial wafer of conventional GaN-based devices by laser-induced Zn doping. Improvement of the photoelectric property of light-emitting diodes LED is confirmed. Compared with LED with no laser-induced doping, the forward voltage under 20 mA current is decreased from 3.33 V to 3.13 V, the series resistance is decreased from 30.27 Ω to 20.27 Ω and the degradation coefficient at room temperature is reduced from 1.68×10-4 to 1.34×10-4. In addition, the reverse leakage current of the LED is reduced from over 0.2 μA to less than 0.025 μA after an aging time of 1600 h by accelerated lifetime testing, and the lifetime is increased about 41. These results are attributed to the improvement of p-type ohmic contact and the decrease of the thermal resistance due to laser-induced doping of Zn to the p-GaN contact layer.