Improving the Current Spreading by Fe Doping in n-GaN Layer for GaN-Based Ultraviolet Light-Emitting Diodes

GaN-based light-emitting diodes (LEDs) grown on the insulating sapphire substrate suffer from a severe current crowding effect. To alleviate the current crowding effect, we demonstrate a current spreading structure for 365-nm ultraviolet LED using Fe doping in n-GaN layer. The surface morphology was studied by atomic force microscope, and the crystal quality was evaluated by high-resolution X-ray diffraction, which shows that a thin insertion layer doped with Fe has less influence on the crystalline quality. Additionally, inserting a Fe-doped layer with appropriate doping concentration enables to induce a barrier in the n-type layer, which contributes to the uniform current distribution. As a result, compared with conventional LED, the light output power obtains a 170.6% enhancement at 100 mA. Furthermore, the uniform optical emission distribution is also achieved by inserting a Fe-doped layer. Finally, the conduction band structures and horizontal hole concentration distributions are calculated by Advanced Physical Models of Semiconductor Devices, which illustrates the mechanism of current spreading.