Semiconductor yellow light LED technology breakthrough

After 57 years of development, is made up of visible light LED full-color, for human visual feast of colour profusion and high efficiency and energy saving lighting source. But for a long time, colorful LED lights, Optical power efficiency) Development is not balanced, the yellow LED luminous efficiency is much lower than other color, the high photosynthetic efficiency of yellow light have to through the phosphor wavelength conversion. This & other; Electro-optical light & throughout; Conversion technology scheme is the mainstream LED lighting technology. Phosphors but big there are heat losses in the process of light conversion, thermal droop congenital deficiencies such as larger, slow response, restricted the LED lighting with high quality and high visible light communication direction of rapid development.

so, solve & other; Yellow light gap & throughout; Problems, become attractive goal in this field. With what kind of substrate, what kind of material, what kind of device structure, what kind of chip structure, what kind of equipment to manufacture high photosynthetic efficiency of yellow light LED? At home and abroad long-term no answer.

figure 1 yellow LED semiconductor electroluminescent

in the two kinds of yellow light material system, AlGaInP with shorter wavelength from red to yellow, from direct to indirect band gap, efficiency fell sharply, this belongs to physical bottlenecks; And indium gallium nitrogen is direct band gap, the biggest difficulty is high quality, high indium composition of indium gallium n quantum well material, which belongs to the technical bottleneck. Yellow LED the indium components of quantum well is about 30%, significantly more than blue light quantum well about 15% of indium composition. High indium composition of indium gallium n growth there are many difficulties: low temperature ammonia cracking caused by less nitrogen vacancy, atomic migration more slow and rough surface, interface trap base fuzzy and different thickness uneven and indium composition, serious when separating indium segregation, InGaN/GaN strong polarization less carrier wave function overlap, and so on.

feng-yi jiang nanchang university recently Research in Photonics Research on published articles: Efficient InGaN -based Yellow Light - Emitting Diodes, shows the yellow band LED material design and manufacturing technology breakthrough. In their original GaN/Si blue LED material, device structure, the structure of the chip, on the basis of design a new structure material, the growth of new equipment and new technology. They put three mismatch ( Coefficient of thermal expansion mismatch, band gap width mismatch, lattice constant mismatch) Into three advantages.

the team created a grid material growth method and technology of grid to replace the rules of the substrate manufacturing have irregular crack, eliminates the GaN/Si stress accumulation effect, solved the material because the problem of crack to manufacture light emitting chip, also by keeping GaN tensile stress and has high growth performance of indium gallium indium composition nitrogen material advantages.

researchers through regulating current, light position, the light path, invented the high efficiency of silicon-based light LED chip structure, both to solve the problem of substrate and electrode block light absorption, also has a single out the advantage of light, high beam quality. To develop a new type of comprehensive transition layer, not only solved the difficult problem of high dislocation density, and rational utilization of dislocation formation with big V pit device structure, improve the hole transport ways, raise the efficiency of leds.

in turn three mismatch on the basis of the three major advantages, they control the reaction gas transport way and the deposition mechanism, invented the dense concentric sleeve structure reaction cavity, developed a more conducive to indium into high indium composition of indium gallium nitrogen equipment material growth, promoted the growth of the material temperature, reduce the memory effect, make the quantum well and the base interface steep; In the 20 A/cm2 and 3 A/cm2, driven by current density of 565 - nm silicon yellow LED light efficiency increase to 24. 3% and 33. 7%, corresponding to 149 lm/W and 192 lm/W, so as to effectively alleviate the yellow light gap, solved the international LED high photosynthetic efficiency of yellow light deficiency problems.

the material structure is brought up with 3 d P - V pit N junction silicon substrate indium gallium nitrogen multiple quantum well structures, chip is single out the light, thin film structure. Figure 2 for the high photosynthetic efficiency silicon InGaN yellow light LED and a combination of silicon substrate AlGaInP red light LED new LED street light, color temperature 2190 k with module, show that 66, 143 lm/W warm color attune, the characteristics of the phosphor powder.

figure 2 red yellow mixed light warm color to move without phosphor new LED street lamp application example

the street lamp combines the advantages of the traditional high pressure sodium lamp warm color to move, and fluorescent type LED street light energy-saving advantages; Saves rare earth resources, speed up the response speed of light, also to avoid the fluorescent type rich blue LED street light the light of the health risks, reduce the light pollution, build a warm and healthy road lighting atmosphere.

high photosynthetic efficiency of yellow light LED manufacturing technology breakthrough, the fine adjustable high quality LED lighting and high-speed optical communication in the areas of development is of great significance.