Demonstration of GaN-based white LED grown on 4-inch patterned sapphire substrate by MOCVD

A blue light emitting diode (LED) chip has been facilely fabricated on a 4-inch patterned sapphire substrate based on an InGaN/GaN multiple quantum well structure, composed of a Ce3+ doped Yttrium Aluminum Garnet (YAG) yellow phosphor packaged into a white LED chip. The epitaxial growth, fabrication, and package process of the device have been briefly described; the structural properties and device performance have also been systematically studied. The surface morphology of the sample in a whole wafer has a good uniformity. And the curvature distribution with a maximum value of similar to 70 mu m, it gradually becomes smaller from the middle to the periphery, which is mainly resulting from the strain state evolution during the film growth. When increasing the injection current, it is significant interestingly observed in the electroluminescence (EL) spectrum that the blue light peak is blue-shifted, it is due to the influence reducing of the polarization field and/or the energy band filling, while the blue light peak and the yellow-green light peak are red-shifted due to the thermal effect of the chip. In addition, the light output power exhibits a linearly incremental relationship with a little saturation when the injection current varies from 0 to 100 mA. Therefore, it is firmly believed that the corresponding chip fabrication and characterization technology will play a certain role in promoting the development of solid-state lighting field.