CS Industry Awards  Winners 2011


Substrates & Material Award Sumitomo Electric Industries, Ltd


The world’s first 6-inch diameter GaN


(gallium nitride) substrates to be used for white LEDs (light emitting diodes)


The white LED market has been growing rapidly using 2- to 4-inch diameter sapphire substrates. It has also been developing larger diameter GaN substrates. These materials allow for better thermal dispersion which will enable LED manufacturers to reduce chip sizes and increase output power.


The company also believes GaN substrates will be used for power devices because of the excellent thermal conductivity, electric responsiveness and breakdown voltage of devices made using these materials.


The front face of the newly developed 6-inch GaN substrates is a polarized*1 c-plane*2. The company has ongoing development efforts to bring this material into large scale production and expects that these materials will find wide-spread use for both white LEDs and power devices


*1 Polarity: Polarity refers to a change in the electrical characteristics of a crystal caused by the preferred orientation of the constituent elements.


The characteristics of a GaN substrate are determined by the orientation of Ga (positively charged) and N (negatively charged). When either element is oriented on the crystal surface, charge distribution within the crystal becomes inhomogeneous, resulting in a decrease of the efficiency.


*2 c-plane: c-plane is a crystal face of a GaN substrate generally used for white LEDs and blue-violet or blue lasers. With positively-charged Ga and negatively- charged N oriented alternately, c-plane exhibits a strong polarization. This polarization decreases light-emitting efficiency in the green region.


Editors Comment: Sumitomo’s development of 6-inch GaN is a really important advance, promising to drive down manufacturing costs for lasers, power electronics and cutting-edge LEDs.


26 www.compoundsemiconductor.net June 2011


WINNER


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