South Korean scientists use buried photonic crystals to increase LED luminescence

South Korean scientists said the day before, in the manufacture of silicon lattice photonic crystal LED, deeply rooted is the key to it, while improving the light extraction efficiency of the electronic properties. The position of the LED photonic crystal is displaced from the top to the active layer, so that the crystal dislocation can be reduced without sacrificing the advantage of light extraction. These are the major findings from Samsung and Kwangju Institute of science and technology researchers, they will be published in June 26th this year, the Applied Physics Letters papers. They prepared the silicon oxide photonic crystal lattice on the LED layer of n-GaN, which is better than the usual p-GaN layer, avoiding the damage from plasma etching. Compared with the LED without the growth of the photonic crystal lattice, the new method reduces the dislocation and improves the efficiency of light extraction, and the two advantage leads to an increase of EQE (70%).

The internal quantum efficiency and the luminous efficiency of the new product were increased by 17% and by PL method, respectively. The output of the two x 300 x m devices is higher than that of the photonic crystal LED () when the drive current is 20mA (). It is reported that IQE is affected by spiral n-GaN and MQW layer reduction reaction and side effect of crystal dislocations, enhance the quality of reducing leakage current of common photonic crystals; in the premise of reducing electric performance, significantly improve the light emitting efficiency of buried photonic crystal LED. On the sapphire substrate, the South Korean team in the n-GaN 2 m layer grown on a silicon oxide layer in a 130nm; using holographic etching method in the layer etched photonic crystal, thereby generating a columnar structure with diameters in the range of 130-230nm. The etching process is a commonly used plasma dry etching method, but the p-GaN layer will be subject to plasma damage, it is confirmed that it will penetrate the entire device to affect the multi quantum well (MQW) layer, and then reduce the performance of LED. In the MQW growth before the use of holographic etching method can be a clever solution to this problem.

The thicker n-GaN layer is more suitable for etching the photonic crystals with ideal size than the thinner p-GaN layer without destroying the performance of LED. At the same time, the silicon oxide layer is lowered to the lower layer of the epitaxial structure, and the effect is similar to that of the silicon grating in the lateral epitaxial (ELOG) method, which is used to produce the high quality GaN crystal layer.

Source: LED chip network