Sumitomo Electric Industries develops a 2-inch semi-/non-polar surface GaN substrate
The blue LED chip used in the white LED and the blue-violet semiconductor laser used in the blue light source are expected to greatly improve the performance of these GaN-based semiconductor light-emitting elements. In the 28a field, Sumitomo Electric Industries, the largest manufacturer in Japan, recently realized the enlargement of the new GaN substrate and is about to launch its products. This product is a GaN substrate with a diameter of 2 inches using a "semi-polar surface" and a "non-polar surface" of GaN crystal. Among them, the substrate with non-polar surface is scheduled to be supplied in 2010.
This substrate product achieved the same level of 105 cm-2 dislocation density as the GaN substrate product used to fabricate the blue-violet semiconductor laser, while expanding the aperture to the same 2 inches as the existing GaN substrate product. The semi-/non-polar GaN substrates previously provided in the industry are small and narrow rectangular products.
A GaN-based semiconductor light-emitting device generally utilizes a crystal face called a "polar face" in GaN crystal. If a semi-/non-polar surface different from the crystal plane is used, the influence of the "piezoelectric electric field" generated in the GaN crystal can be weakened, which contributes to the improvement of the light-emitting efficiency of the light-emitting element and the extension of the wavelength (Fig. 1). . For example, by using a non-polar surface, it is expected to increase the luminous efficiency by more than 20%. In addition, since the wavelength is easily extended, a pure green semiconductor laser can also be realized.
Although Sumitomo Electric Industries did not disclose the details of the implementation technology, it is said to achieve a 2-inch substrate diameter by using the self-developed HVPE method. The HVPE method itself is a technology used by existing GaN substrate products. Therefore, it is possible to make full use of existing manufacturing equipment. That is to say, it is expected to achieve the same price as the existing GaN substrate products.
6-inch products will also be unveiled
However, the price of GaN substrates is higher than that of Si substrates and sapphire substrates, and the aperture is much smaller, so they are mainly used in the field of lasers. Sumitomo Electric Industries intends to overcome this problem and promote the adoption of GaN substrates in LEDs and power semiconductors.
Therefore, Sumitomo Electric Industries is working on further enlargement of GaN substrates. Unlike the semi-/non-polar surface described above, the same polar surface as the existing GaN substrate is used, and the successfully developed large-sized substrate realizes a 6-inch aperture. With the appearance of large-sized products that contribute to increase in production efficiency, the cost per unit element of blue LED chips, semiconductor lasers, and power semiconductors using GaN substrates is expected to be lowered.
Figure 1: Advantages of a semi/nonpolar GaN substrate:
By using a half/nonpolar surface GaN substrate for the light-emitting element, the internal quantum efficiency can be improved and the wavelength can be extended. For example, if the internal quantum efficiency is improved, a highly efficient blue LED can be realized.
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