Enhancing light extraction efficiency of GaN LED by combining complex-period photonic crystals with doping

The light extraction efficiency (LEE) of GaN-based light-emitting diodes (LEDs) was limited by intense total internal reflection and the photothermal effect. In order to solve this problem, a method to synergistically control the LEE of GaN-based LEDs by ​​combining the complex-period photonic crystals (PhCs) with M (M = Al, In) material doping is proposed. The forbidden band width of two-dimensional (2D) PhC array, three-dimensional (3D) LED model, M doping, and electromagnetic field distribution are investigated respectively. By doping the M, the LED emission wavelength range is regulated to achieve the dual-band emission. Furthermore, a triangular complex-period photonic structure is introduced to establish stacked or etched PhCs models. By combining the plane wave expansion and finite difference time domain algorithm, the structural parameters of PhCs and M concentration dependent LEE are investigated, and the electromagnetic field distribution is explored also. The results show that the optimal LEEs can be achieved are 19.08% and 13.96% for blue light and ultraviolet, respectively, which are larger than that of traditional flat-panel LED (4%). This work provides theoretical results and technical support for the design of LEDs with high luminous efficiency.