The LED consists of (1) a blue LED chip made on a β-type Ga2O3 substrate by using GaN-based semiconductor and (2) a fluorescent material. Compared with a case where a common blue LED chip formed on a sapphire substrate is used, the new LED realizes a higher optical output, the companies said.
At the show, Tamura and Koha showcased two kinds of white LEDs that use 0.3 x 0.3mm and 2 x 2mm blue LED chips, respectively. Their driving currents are 400mA and 6A. The brightness of the LED using the 2 x 2mm chip is about 500lm. And the companies aim to increase it to 2,000 to 3,000lm, which is difficult to realize by using a sapphire substrate, they said.
With a blue LED chip formed on a sapphire substrate, it is necessary to use the "horizontal structure," in which anode and cathode electrodes are horizontally arranged because a sapphire substrate is an insulator. On the other hand, a β-type Ga2O3 substrate has a high electrical conductivity and allows to use the "vertical structure," in which anode and cathode electrodes are formed on the top and bottom sides of an LED chip.
Compared with the horizontal structure, the vertical structure makes it easier to reduce element and heat resistances and to realize an even current distribution. The smaller the element and heat resistances, the smaller the amount of heat generated by an LED chip. Therefore, the new LED is suited to be driven by a high current.
Though GaN substrates are also suited for making high-output LEDs, β-type Ga2O3 substrates realize lower costs, Tamura and Koha said. Currently, GaN substrates are manufactured by using a vapor-phase epitaxial method called HVPE. On the other hand, β-type Ga2O3 substrates are manufactured by the melt growth method, which is theoretically suited for improving the quality of substrate and increasing substrate size.
The diameter of the β-type Ga2O3 substrate that has already been commercialized is 2 inches. The companies plan to prototype a 4-inch product within 2014 and commercialize it in 2015. They will also try to develop a 6-inch product.
About Tamura Corp:
Tamura is a world-class manufacturer of high quality electronic components for global markets. With 2011 sales greater than 900 Million US Dollars, Tamura Corporation is one of the largest suppliers of magnetic components and power supplies in the world. Publicly traded on the First Section Market of the Tokyo Stock Exchange, Tamura has proven financial strength, innovation and ability to grow for more than 80 years. Tamura's state-of-the-art manufacturing facilities in Asia, Europe and Mexico support leading edge technologies for the future's high demand applications.
About KohaCo. Ltd:
Founded in 1985 as an "optoelectronics engineering company," KOHA Co.,Ltd. develops optoelectronic products incorporating LEDs. We provide our products for deployment in many fields, including the chip LED lamps used in cellular phones and various OA equipment, and numerous types of traffic displays used in railway and road safety. Our self-illuminating interlocking pushbuttons, featuring built-in switches for vending machines, dominate the market.
Since the public offering of our stock in 1998, KOHA has been involved in the development of products using LED features in new fields such as lighting devices and illumination, in addition to our core products.
We take pride in our approach to exploring the possibilities of optoelectronics by using our sophisticated knowledge and advanced LED technology,and actively developing innovative and marketable products in a timely manner. Our greatest assets are the partnerships we have built with our customers.
The market for products incorporating LEDs will see further expansion.
Employing the pioneering spirit that has been our hallmark since KOHA’s establishment, we will enhance our R&D and marketing capabilities, as well as employee training and management innovation.
These activities establish the cornerstone of KOHA, which is the effective provision of solutions that meet the expectations of our customers and market.
