Biruza

Appeared in 1996 on the market blue LEDs produced by epitaxy from the gas phase at geterosubstrate (usually in single-crystal sapphire). The difference in the properties (in particular, the coefficient of thermal expansion) between the besieged and the substrate layer leads to the fact that grown at 800 ? C layer on cooling to room temperature cracking. The high density of dislocations in a layer (104-106 cm-2) leads to a sharp decline in service quality of the material: the term of service, the percentage of marriages, luminous, monochromaticity, etc. Top-emitting diodes are less than 2 years of continuous light. Proposed monocrystalline GaN will have on the orders of fewer defects (solution-rasplavny GaN, resulting in small numbers in Warsaw, has a 102 dislocations per square centimeter). Single crystals of gallium nitride would be an ideal substrate for epitaxial films of increasing GaN, as well as a boule of silicon is now a substrate for the production of multi-electron systems (diodes, transistors, microprocessors, etc.).So far, the largest crystals of GaN (plate width of 10-20 mm and a thickness of 0,1-0,2 mm) were grown from the melt is: from the solution of Ga in the Na (at a pressure of nitrogen 30-50atm and 750-800 ? C) or from the melt of pure gallium (1000 5000atm and 1300-1500 ? C). This underlines the promising method.Russian development relate primarily to the epitaxial growth of the gas phase, repeating, and in some cases, ahead of the experience of foreign colleagues In the synthesis of GaN rasplavnogo chelyabinsk group, apparently, is the first group in Russia, began the project.