A method of combining the AlGaN/GaN superlattices and Mg delta doping was proposed to achieve a high conductivity p-type GaN layer. The experimental results provided the evidence that the novel doping technique achieves superior p-conductivity. The Hall-effect measurement indicated that the hole concentration was increased by 2.06 times while the sheet resistivity was reduced by 48%. The fabricated green-yellow light-emitting diodes using the achieved high conductivity p-type GaN layer showed an 8- and 10-times enhancement of light output power and external quantum efficiency, respectively. The subsequent numerical calculation was conducted by using an Advanced Physical Model of Semiconductor Device to reveal the mechanism of enhanced device performance. This new doping technique offers an attractive solution to the p-type doping problems in wide-bandgap GaN or AlGaN materials.

In this paper, a method of indium-tin oxide/Au/indium-tin oxide (IAI) structure as transparent conductive layers (TCLs) to improve the current spreading and suppress efficiency droop of ultraviolet light-emitting diodes (UV-LEDs) is investigated. The morphology and distribution of Au clusters formed by annealing are investigate by atomic force microscope and scanning electron microscope. Compared with the UV-LED without Au clusters, the forward voltage of UV-LED is reduced by 5.9% at 20 mA, light output power and wall plug efficiency increase by 64.2% and 84.2% at 300 mA for the UV-LED with IAI structure as the thickness of the Au interlayer is 1 nm. In addition, light emission distribution results show that by inserting Au interlayer, current distributes more uniform and the current spreading characteristics of UV-LED are improved. Ultimately, efficiency droop of the LED has been suppressed.

A method to improve the performance of ultraviolet light-emitting diodes (UV-LEDs) with stair-like Si-doping GaN layer is investigated. The high-resolution X-ray diffraction shows that the UV-LED with stair-like Si-doping GaN layer possesses better quality and a lower dislocation density. In addition, the experimental results demonstrate that light output power and wall plug efficiency of UV-LED with stair-like Si-doping GaN are significantly improved. Through the analysis of the experimental and simulation results, we can infer that there are two reasons for the improvement of photoelectric characteristics: reduction of dislocation density and alleviating of current crowding of UV-LEDs by introduced stair-like Si-doping GaN.