Study Of The Surface Treatment Effect On Roughness And Light Extraction Efficiency Of GaN-based LEDs On Si Substrate

As the prompt improvement of LED technology, the high-power LEDs have been developed to the market of ordinary illumination. The white light luminous efficiency of the Laboratory data has been known up to2401m/W, while the blue LEDs luminous efficiency in the actual production applications are generally more than160lm/W. The GaN-based LEDs grown on the Si substrate, due to its low cost, good thermal conductivity and other advantages, in combination with the substrate transfer technology and Ag reflection mirror as well as surface roughness, have successfully applied to the high-power TF-structure chips, which have been developed to the commercialize stage, have been a potential and highly competitive technology roadmap. As known to all, the most direct and effective way to improve the light extraction efficiency of the LEDs is the surface roughening technology, the implementation of which is the surface of N-polar GaN become rough with KOH solution wet corrosion. However, wet etching rate related to many factors is often difficult to control, therefore, how to get a ideal rough surface has become a key issue to improve the efficiency of LEDs. In this paper, the surface roughing technology of the Si substrate GaN-based high-power LEDs has been studied, using both of the surface treatment methods, dry etching and wet etching. The results are as following:1.The effect of AIN buffer layer on n-GaN surface roughening has been studied. If not do any processing, the etch rate of AIN is very slow, difficult to form the ideal six pyramid rough surface. If AIN is all removed, the etch rate of roughing is too fast. If the AIN buffer layer is moderately dry etched, then wet etched with KOH solution, we can get the best roughing surface morphology.2. This article uses the XPS to image the surface features of the different etching treatment before surface roughness. The results are that the treatment of the freon plasma ICP-RIE can effectively remove the residual Si on the surface, the Fermi level of the AIN surface shift to higher so that the work function decreases, which is benefit to the surface roughing, but it will also introduce the F ions and the surface oxide, which could be removed using HC1solution to treat the surface. The sulfuric acid hydrogen peroxide corrosion of AIN buffer layer can not remove Si and its compounds, and has no great effect on the Fermi level.3. This article uses the SEM to image the rough surface morphology. The results is that, some degree of dry etching, as long as the AlN buffer layer can significantly improve the Si substrate surface roughening effect of the LED chips, the optical power of the bare core of the corresponding device will have significantly improved.