Wafer technology and equipment are the key to epitaxial wafer manufacturing technology. Metal-Organic Chemical Vapor Deposition (MOCVD) technology is the main method for growing thin-layer single crystals of III-V and II-VI compounds and alloys. . Below and everyone to introduce the light knowledge of LED epitaxial wafer growth technology related information.

      1, hydride vapor phase epitaxial (HVPE) technology

  With this technique, a thick film with low meta-error density can be quickly grown, and can be used as a substrate for homoepitaxial wafer growth using other methods. In addition, the GaN thin film separated from the substrate may be a substitute stage lighting for the bulk single crystal GaN chip.

The disadvantage of HVPE is that it is difficult to precisely control the film thickness, the reactive gas is corrosive to the device, and the purity of the GaN material is further increased.

      2. Development of UVLED epitaxial wafer material with short wavelength

      It lays a solid foundation for the development of UV trichromatic phosphor white LEDs. There are many high-efficiency fluorescent powders that can be excited by UV light, and their luminous efficiency is much higher than that of the currently used YAG:Ce system, which makes it easier for white LEDs to reach 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 a time is limited, 6 machines are relatively mature, and about 20 machines are still matured. After a large number of sheets, the homogeneity of the epitaxial films is insufficient. The development trend is in two directions: first, development can increase the number of substrate wafers grown in a reaction chamber at a time, which is more suitable for large-scale production technologies to reduce costs; and the other direction is highly automated repeatability. Monolithic device.

      4, the development of "photon recirculation" technology

      Sumitomo Japan developed a white LED of ZnSe material in January 1999. The technique is that a layer of CdZnSe film is first grown on the ZnSe single crystal substrate, and the blue light emitted by the film is combined with the substrate ZnSe to emit complementary yellow light after electrification, thereby forming a white light source. In the same way, the Photon Research Center of the University of Boston, USA stacked a layer of AlInGaP semiconductor compound on a blue GaN-LED and also generated white light.

      5, Pendeo-epitaxy technology

      With this method, a large number of lattice defects in the epitaxial wafer layer due to the lattice mismatch and thermal mismatch between the substrate and the epitaxial wafer layer can be greatly reduced, thereby further improving the crystal quality of the GaN epitaxial wafer layer. First, a GaN epitaxial layer is grown in a two-step process on a suitable substrate (6H-SiC or Si). Then, the epitaxial film is etched in a selected region until it reaches the substrate. This forms the columnar structure of the GaN/buffer layer/substrate and the alternating shape of the grooves. Then, the GaN epitaxial layer is further grown. At this time, the grown GaN epitaxial layer is suspended above the trench and is grown on the lateral epitaxial wafer of the original GaN epitaxial layer. With this method, no mask is needed, thus avoiding contact between GaN and the film material.

      6, selective epitaxial wafer growth or lateral epitaxial wafer growth technology

      Using this technique can further reduce the bit error density and improve the crystal quality of the GaN epitaxial layer. First, a layer of GaN is deposited on a suitable substrate (sapphire or silicon carbide), a polycrystalline SiO mask layer is deposited thereon, and then lithography and etching techniques are used to form a GaN window and a mask layer. Article. In the subsequent growth process, the epitaxial wafer GaN is first grown on the GaN window and then grown laterally on the SiO strip.

      7. Develop multiple quantum well chip technology

      The multi-quantum well type is in the process of growing the light emitting layer of the chip, doping different impurities to make quantum wells with different structures, and directly emit white light through multiple photons emitted from different quantum wells. The method improves the luminous efficiency, can reduce the cost, and reduces the difficulty of controlling the packaging and the circuit; but the technical difficulty is relatively large.

      Second, how to adjust the light control

      Dimming control is usually to change the size of the current through the lamp, in order to adjust the brightness of the lamp brightness. Divided by dimming method: varistor dimming, auto-transformer regulator dimming, saturation choke dimming, magnetic amplifier dimming and SCR dimming. The first four dimming devices have the disadvantages of large size and bulkiness. Thyristor dimmers are widely used today.

      The control of KTV lighting is basically achieved through these two methods. It is noticed that different changes will achieve the ever-changing effects, different combinations, different decoration methods, different materials, and different control methods. Not the same ~!