Study On Enhancement Of Internal Quantum Efficiency Of GaN-based Green LED With Nano Column Structure

GaN-based light emitting diode(LED) with nanocolumn structure has unique properties, such as surface effect and small size effect, and has good optical properties. Therefore, nanocolumn LED is a hot topic in recent years. Using colloid microspheres as photolithography mask, Nanocolumn green LED was fabricated by inductively coupled plasma(ICP) and its optical property was anaylied. The main work is as follow.An important step to get high efficiency nanocolumn LED is the formation of an orderly arranged mask. The spin-coating method, liquid dropping method, and gas-liquid interfacial method were used in colloidal microspheres self-assembly experiment. The morphology was observed by SEM, and the advantages and disadvantages of these three methods were analyzed. It shows that the gas-liquid interface method is suitable for the preparation of single layer compact colloidal microspheres mask.SiO2 nanoparticles were formed by self-assembly colloid microspheres. ICP dry etching method was used to fabricate the nanocolumn structures with three different heights in GaN-based green LED epitaxial wafers, and the nanocolumn structure’ morphology was observed by SEM. The photoluminescence(PL) spectra were used to analyze the luminous properties of these three kinds of nanocolumn structure. Compared with the ordinary planar structure, the nanocolumn structure with the height of 747 nm induces an enhancement of 917 % for the IQE, an 18 nm blue-shift for the peak wavelengths of PL spectrum, and a broadening of 7 nm for the FWHM.Ag nanoparticles were inserted in nanocolumns and the surface plasmon can be excited near the LED quantum well. The spontaneous emission rate of quantum well would be enhanced and the internal quantum efficiency can be improved. A surface plasmon assisted LED with nanocolumn structure whose depth is 680 nm, its internal quantum efficiency can reach 55.6 %, and the high efficient LED is realized.