Shimei Semiconductor grows blue LED on silicon wafer

Using silicon wafers as a substrate for GaN epitaxy could drastically lower the cost, simplify LED structure, extend the lifetime and enable the integration of an optical device in CMOS circuits, the company claims.

The prototype LED emits blue light of the 450-nm wavelength and an output power of 10 mW. Shimei said it expects to improve performance through future prototyping. LED lifetime was disclosed. Currently, sapphire substrates are widely used for GaN ataxia growing. If silicon wafers can be used for the substrate of GaN crystalline deposition, “silicon wafers have a lot of advantages [and] it is easy to make large area LEDs, and drivers and other circuits can be fabricated on the same silicon substrate,” said Hirofumi Yamamoto, founder and chief technology officer of Shimei Semiconductor (Kyoto, Japan).

The device has a layered structure consisting of a cathode on the bottom, the silicon substrate, buffer layers, an emitting layer and an anode on top. As the silicon substrate absorbs light generated at the emitting layer, a reflective film is formed on the silicon to improve efficiency.”