Research Of Improving Extraction Of LED Based On Porous Structure

Since the act of commercializing LED (light-emitting diode) in 1960s, LEDs have been attracting more and more attention. How to improve the extraction efficiency of LEDs also becomes a hotspot in the current research field. In this work, the porous structure was prepared by lithography and Nano-imprint. and optical properties of samples were studied.The micron-grade porous structure was fabricated on monocrystaline silicon by lithography. Photoluminescence (PL) of the samples was measured by fluorescence spectrometer at room temperature. The diameters of porous structure includes 2μm and 6μm, and the hole spacing was 6μm and 8μm respectively. Depth of 70nm,140nm and 260nm was etched by RIE(Reactive Ion Etching). The surface and cross profile of porous structure was measured by FSEM (Field Scanning Microscope). Intense photoluminescence of porous silicon was observed at 425nm and 473nm. The intensity of the luminescence peak was stronger when exciting wavelength was 270nm, compared with 280nm.The micron-grade porous structure was fabricated on P-GaN layer of blue MQW (Multiple Quantum Well) LED by lithography and ICP (Inductively Coupled Plasma). The diameter of porous structure was 2μm, hole pitch was 6μm and depth of 70nm was etched. The surface morphologies were observed by using metalloscope and PL of samples was measured by fluorescence spectrometer. Result shows that the PL intensity of porous structure LED was improved by 30%, compared with standard LED, and extraction efficiency was enhanced by 10% after encapsulation.Anodic aluminum oxidation (AAO) was fabricated by anodic oxidation method. The micron-grade porous structure was transferred on P-GaN layer of blue MQW LED by Nano-imprint and ICP. The surface morphologies of AAO and samples were observed by FSEM and AFM (Atomic Force Microscope).