| Ga N-based LED as the illumination photosource is both energy saving and environmental friendly. It has opened up a new era of human illumination and has been closely linked with people’s lives so that the Nobel physics prize was awarded to the relevant research achievement of Ga N-based LED in 2014. At present, the commercialization of Ga N-based LED epitaxial substrate is divided to three technical routes which include silicon carbide(Si C), sapphire(Al2O3) and silicon(Si) substrate. The sapphire substrate LED market share was biggest. The silicon carbide substrate LED market share was second. Although the silicon substrate LED market share was smallest, its market share is gradually expanding and applications are becoming more widespread. Although the technical route of silicon substrate has some limitations and it is unclear whether it will become a mainstream technology in the future, it has become a hot research area in LED field because of it has many significant advantages. Silicon substrate can absorb visible light and there is a huge tensile stress in Ga N-base LED film because of the large lattice mismatch. So the practical LED chip of silicon substrate is transferred to the new supporting submount into a vertical structure chip by methods of bonding and wet etching. There is a huge tensile stress in silicon substrate Ga N-based LED film and a certain degree stress was released has been reported after the film transferred to the new submount. However, whether the silicon substrate Ga N-based LED film can be bonding process after releasing the tensile stress to produce vertical structure chip and the photoelectric performance of the chip will be improved has not been reported so far.Although three technical routes of the vertical structure LED chip are commercially available and widely used and small changes about stress will obviously influence photoelectric performance of Ga N-based LED after transferred to the new submount, there is not study about how to make the chip play the best photoelectric performance when the Ga N-based LED film transfer to the new supporting submount.The same epitaxial structure of Ga N-based green light-emitting diode(LED) thin films grown on Si(111) substrate were successfully bonded and transferred onto new silicon supporting submounts by methods of the directly bonding process and bonding process after releasing the tensile stress. New silicon supporting submounts were deposited by two kinds bonding metal. Then, four kinds vertical structure LED chips with different non-working stress(initial stress) were fabricated. At the same time, we investigated the photoelectric properties of the vertical structure devices deeply. The obtained results are as follows.1、When the LED film adhere submount together by organic flexible bonding layer, after removal of silicon substrate, the tensile stress of LED film will be released in full suffer from the silicon substrate.2、The high resolution XRD shows that the residual tensile stress of Ga N films decreases when it is transferred to new silicon submounts. And there is more significantly decrease of tensile strress when the chips fabricated by bonding process after releasing the tensile stress of the LED thin film. There is only small decrease of tension stress when the chip fabricated by directly bonding process3、In the process of Si substrate vertical structure Ga N-based LED chips, the tensile stress of the chip fabricated by directly bonding process will gradually decrease, and then, the chip fabricated by bonding process after releasing stress is just the opposite.4、The luminescence property of vertical structure LED chips will not only influenced by initial stress of LED film but also the different bonding metal.5、The well layer of the chip fabricated by bonding process after releasing stress has larger compressive stress than the chip fabricated by directly bonding process, however, by EQE normalization process, four chips have the same current Droop effect. |
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