"For large area GaN LED 1m square in the East high carbon film laminated GaN

Fujioka Yo, a professor at the Institute of production technology, University of Tokyo, and the Kanagawa Institute of science and Technology (KAST) announced the joint development of a flexible substrate formed by gallium nitride (GaN) composed of LED technology. The manufacturing method is used to support the large area and the production of PVD (physical vapor deposition) a, therefore "make 1m square to the low cost of the surface area of GaN LED Everbright is entirely possible" (Fujioka). At present, although the size is only 2cm square, and only confirmed the UV light excitation, but in a few months will be the same as the LED current excitation luminescence test.

Photoluminescence excitation is confirmed by UV irradiation. The sheet is an organic polymer in 2cm square sintering graphite sheet laminated AlN and GaN films of Neusoft Fujioka researchers such as the GaN LED not use sapphire plate ordinary, instead of using the organic polymer sintering graphite sheet (PGS)". PGS is a thin piece of resin sheet sintered at the temperature of 3000 degrees and oxygen free. The structure of a C atom is formed in a hexagonal shape, which is connected to a surface and is stacked together. Thickness of 25 ~ 100 m. "The extent to which the surface reaches the atomic level" (Fujioka).

Model of the joint surface between the bottom plate and GaN. First, nitrogen (N) is bonded on the carbon (C) grid, and then the GaN crystal is formed on it

It has been confirmed that, in this kind of PGS, the use of AlN developed by researchers such as PVD, so that GaN and AlN (AL) crystal growth, can form a very high quality of crystallization without defects. "The quality of the crystals is comparable to or higher than the commercially available GaN LED, either by X-ray analysis or by luminescence spectroscopy" (Fujioka). In ordinary GaN, there are several emission peaks in the wavelength range longer than the 3.3eV (365nm) wavelength due to the crystal defects. And the product is almost no excess emission peak. The PVD name used in the formation of the GaN film is the pulse excitation stacking method". The method is realized by the self - improvement of the sputtering method made by Fujioka. The specific method is to use pulse plasma to sublimate the metal Ga, and then react with nitrogen. The processing temperature of GaN is 600 to 800 DEG C. "Easy to use in large area products. If you are a manufacturer, you can quickly create a large area of LED (Fujioka). N PGS and GaN C combination that can form Fujioka, high quality GaN crystal in PGS, one of the reasons is composed of hexagonal nitrogen PGS C atoms and GaN in nitride (N) lattice interval atoms are basically the same, the C-C key and PGS combined with the nature of the fixed capture N. "The formation process is that N is first immobilized on PGS, and then GaN crystals grow on it" (Fujioka).

The appearance of the GaN crystallization model on the base of a blue graphite sheet (100 m thick) used as a substrate

Because PGS "high thermal conductivity, is 4 times the copper (Cu), it is often used as PC heat sink, and compared with the sapphire substrate is quite cheap" (Fujioka). Moreover, the utility model has the characteristics of thin, soft and high heat resistance, and therefore, the utility model has the advantages of low cost, large area and thin, soft film like cloth. High priced materials known as gallium (Ga), as long as the thickness of 1 m or less, even a large area is only a very small number (Fujioka). Fujioka, etc. will be held in March 2008 27 to 30, the Institute of Applied Physics, the fifty-fifth Academic Conference on the details of the technology announced

Source: Nikkei BP