The Led Wafer Technologies Of The Future Development Tendency

Works we can see from the LED, LED wafer material is the core of fact, LED wavelength, intensity, forward voltage and other major optical parameters depends largely on the wafer material. Wafer technology wafer manufacturing technology and equipment is the key, metal organic chemical vapor deposition (l-Organic Chemical Vapor Deposition, referred to as MOCVD) growth technology of III-V, II-VI compounds and alloys of thin single crystal the main method. Here are some LED wafer technology future trends.

1. Improved two-step growth process
At present, commercial production is used in two-step growth process, but a limited number of substrates can be loaded, six machine more mature, 20 mature about the machine is still in pieces after a few more leading wafer uniformity is not enough. The trend is in two directions: First, develop a reaction chamber in a substrate wafer into more growth, more suitable for large-scale production technology to reduce costs; the other direction is highly automated repeatability single-chip devices.

2. Hydride vapor phase wafer (HVPE) technology
Using this technology can quickly grow out of the thick low dislocation density, the use of other methods can be used for homogeneous growth substrate wafer. And the separation of GaN film and the substrate may become a body of single crystal GaN chip alternatives. HVPE disadvantage is difficult to precisely control the thickness, the reaction gas is corrosive to the equipment, affecting the purity of the further improvement of GaN materials.

3 selective growth or lateral wafer wafer growth technology
Using this technology can further reduce the dislocation density, improve the quality of GaN crystal wafer layer. First, in a suitable substrate (sapphire or silicon carbide) deposited a layer of GaN, and then in its polycrystalline layer deposited on the SiO mask layer, then using lithography and etching techniques to form a GaN layer window and mask section. In the subsequent growth process, the first GaN GaN wafers grown on the window, and then grown in SiO horizontal bar.

4 floating wafer technology (Pendeo-epitaxy)
This approach can greatly reduce the substrate and lattice mismatch between the wafer layers and thermal mismatch induced wafer layer in a large number of lattice defects, thus further improving the quality of GaN crystal wafer layer. High-power LED lights with conventional high pressure sodium lamps is different is that high-power LED street light low voltage DC power supply. First, in a suitable substrate (6H-SiC or Si) two-step growth of GaN wafer process layer. Constituency of the wafer and then etched membrane, has been deep into the substrate. This form of GaN / buffer layer / substrate structure and grooves alternating columnar shape. Then the growth of GaN wafer level, at this time of GaN wafer layer floating on top of the trench is in the original wall of the lateral layer of GaN wafer wafer growth. Using this method, no mask, thus avoiding the GaN and the contact between the membrane material preserved.

5 R & D-wave length UV LED wafer material
It is for the development of three-color phosphor white LED UV laid a solid foundation. UV light excitation efficiency for a lot of phosphor, the luminous efficiency than the currently used YAG: Ce system is much higher, so easy to make white LED on to a new level.

6. Development of multi-quantum well-type chip technology
MQW-based light-emitting layer in the silicon growth process, doping impurities to create a different structure of different quantum wells, quantum well given by a variety of different composite direct white light photons. The method to improve light efficiency, reduce costs, reduce packaging and the circuit difficult to control; but technical difficulty is relatively large.

7. Development "photon recycling" technology
Sumitomo of Japan in January 1999, developed the material ZnSe white LED. Its technology is first grown on ZnSe single crystal substrate layer CdZnSe film, the film after the power to issue Blu-ray and the role of the substrate to issue complementary yellow ZnSe to form white light sources. Boston University Photonics Research Center, the United States the same way in the blue GaN-LED Diego put on a layer of AlInGaP semiconductor compounds, but also generate white light. This technology will also be applied to LED street light.

LED Wafer Processing
Substrate>> design>> buffer layer growth>> N-type GaN layer growth>> multi-quantum well light-emitting layer growth>> P-type GaN layer growth>> annealing>> test (fluorescent light, X-ray)>> Wafer film
Wafer>> design, processing Mask>> Lithography>> ion etching>> N-type electrode (coating, annealing, etching)>> P-type electrode (coating, annealing, etching)>> Dicing >> grain sorting, grading.