From：Rainbow Confetti Co.,ltd Release time：2019-10-29
Overview：The extension technology and equipment are the key to the epitaxial wafer fabrication technology. The main method of growing thin-layer single crystals of III-V, II-VI compounds and alloys by Metal-Organic Chemical Vapor Deposition (MOCVD) technology .
Introduction to LED epitaxial wafer growth technology in lighting knowledge
The extension technology and equipment are the key to the epitaxial wafer fabrication technology. The main method of growing thin-layer single crystals of III-V, II-VI compounds and alloys by Metal-Organic Chemical Vapor Deposition (MOCVD) technology . Let's introduce the stage lighting equipment related to LED epitaxial wafer growth technology in lighting knowledge.
1. Hydride vapor phase epitaxial wafer (HVPE) technology
With this technique, a thick film a low bit error density can be rapidly grown, and can be used as a substrate for homoepitaxial growth using other methods. And the GaN thin film separated from the substrate is likely to be a substitute for the bulk single crystal GaN chip. The disadvantage of HVPE is that it is difficult to precisely control the film thickness, the reaction gas is corrosive to the device, and the purity of the GaN material is further improved.
2. UVLED epitaxial wafer material with short development wavelength
It lays a solid foundation for the development of UV trichromatic phosphor white LEDs. There are many high-efficiency phosphors that can be excited by UV light, and the luminous efficiency is much higher than that of the currently used YAG:Ce system, which makes it easy to bring white LEDs to a new level.
3. Improve the two-step growth process
At present, the commercial production adopts a two-step growth process, but the number of substrates that can be loaded at one time is limited, the six-piece machine is relatively mature, and the 20-piece machine is still mature, and the number of sheets is large, resulting in insufficient uniformity of the epitaxial wafer. The development trend is two directions: one is to develop more epitaxial wafer growth in the reaction chamber at one time, which is more suitable for large-scale production technology to reduce costs; the other is highly automated repeatability. Monolithic device.
4. Develop "photon recirculation" technology
In January 1999, Sumitomo of Japan developed a white LED with ZnSe material. The technology is to first grow a layer of CdZnSe film on the ZnSe single crystal substrate. After energization, the blue light emitted by the film and the substrate ZnSe act to generate complementary yellow light, thereby forming a white light source. In the same way, the Photonics Research Center of the University of Boston in the United States stacked a layer of AlInGaP semiconductor composite on a blue GaN-LED, which also produced white light.
5, suspended epitaxial wafer technology (Pendeo-epitaxy)
By adopting this method, a large number of lattice defects in the epitaxial layer due to lattice mismatch and thermal mismatch between the substrate and the epitaxial layer can be greatly reduced, thereby further improving the crystal quality of the GaN epitaxial layer. The GaN epitaxial wafer is first grown on a suitable substrate (6H-SiC or Si) using a two-step process. The epitaxial film is then selectively etched down to the substrate. This forms the columnar structure of the GaN/buffer layer/substrate and the alternate shape of the grooves. Then, the GaN epitaxial layer is grown, and the grown GaN epitaxial layer is suspended above the trench, and is grown on the lateral epitaxial wafer on the sidewall of the original GaN epitaxial layer. With this method, no mask is required, thus avoiding contact between the GaN and the pickle material.
6. Selective epitaxial wafer growth or lateral epitaxial wafer growth technique
This technique can further reduce the bit error density and improve the crystal quality of the GaN epitaxial layer. First deposit a layer of GaN on a suitable substrate (sapphire or silicon carbide), deposit a polycrystalline SiO mask layer on it, and then use lithography and etching techniques to form a GaN window and mask layer. article. During the subsequent growth process, the epitaxial wafer GaN is first grown on the GaN window and then laterally grown on the SiO strip.
7, the development of multiple quantum well chip technology
The multi-quantum well type is a quantum well doped with different impurities in the growth process of the light-emitting layer of the chip to directly emit white light by a plurality of photon recombinations emitted by different quantum wells. The method improves the luminous efficiency, reduces the cost, and reduces the control difficulty of the packaging and the circuit; but the technical difficulty is relatively large.
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