GaN-based semiconductor LED lighting has the advantages of high efficiency, energy saving, environmental protection, long life and easy maintenance. It is another lighting revolution in the history of human lighting following incandescent and fluorescent lamps. With the development of wearable technology, flexible semiconductor technology will gradually become the mainstream in the future, and the preparation of flexible GaN has become a research hotspot that attracts international attention today.
Due to the high cost of large-sized nitride substrates, nitride films are usually epitaxially grown based on heterogeneous material substrates such as sapphire and silicon. There is a serious lattice mismatch between the crystal substrate and the nitride, which causes a large stress in the epitaxial GaN thin film, and generates a large number of penetration dislocations, which leads to a reduction in the luminous efficiency of the LED device. Therefore, the preparation of low-stress, high-quality GaN films is particularly important for the improvement of LED performance.
At present, laser lift-off technology is the main method for preparing flexible GaN, but uneven laser energy density distribution causes the GaN thin film protrusions to break, and it is difficult to obtain large-area continuous and non-destructive GaN thin films, which seriously hinders the development of GaN flexible devices. .
The team studied and discovered the selective nucleation mechanism of nitride on graphene, found the best nucleation site of AlN, and successfully prepared a high-quality, stress-free GaN epitaxial layer. And by optimizing the lift-off process, low-damage, large-area lift-off transfer of the GaN epitaxial layer is achieved. The violet light-emitting diode prepared based on the flexible GaN material achieves ultra-high light output power at a small current. The research results prove the possibility of peel-off transfer to achieve GaN-based flexible lighting and LEDs to achieve high-quality vertical structures in the future.