Cree Japan, a Japanese unit of Cree Inc, introduced the "XLamp XB-D," a white LED lamp that is smaller and brighter than the company's former product.
The LED lamp was exhibited at the 4th LED/OLED Lighting Technology Expo, which took place from Jan 18 to 20, 2012, in Tokyo. The company realized the small size and higher brightness by employing a newly-developed LED chip.
The footprint of the package is 2.45 x 2.45mm, which is about half that of the former product (3.45 x 3.45mm). With an input current of 350mA, the luminous flux of the lamp is 148lm (when the junction temperature is 25°C), which is higher than that of the former product (139lm).
Even when the junction temperature is 85°C, which is a normal temperature of an LED lighting apparatus in use, the luminous flux of the lamp is about 130lm. Cree started to ship the product in January 2012.
The new LED chip was developed by improving the light extraction efficiency of a blue LED chip. Cree improved the light extraction efficiency by forming several V-shaped ditches on the substrate of the blue LED chip.
Cree calls LED chips using this technology "DA Chip Family." The DA Chip is made by growing gallium nitride (GaN)-based semiconductor single crystals, which will become a light-emitting layer, on a silicon carbide (SiC) substrate and forming V-shaped ditches from the outside of the SiC substrate. Light is extracted from the side having the V-shaped ditches.
Because the side of the light-emitting layer is connected to the package, the heat generated in the light-emitting layer due to light emission can be easily conducted to the package. As a result, it becomes possible to prevent the luminous efficiency from lowering when a large current is used.
Cree Japan showed a road map of the luminous efficiencies of its white LEDs. According to the road map, Cree will achieve a luminous efficiency of 231lm/W in 2011 or 2012 in the R&D level and commercialize a white LED having an equivalent efficiency in 2014. About one year ago, Cree Japan announced that it would develop and commercialize products with efficiencies up to 208lm/W in a road map.