| dc.description.abstract | Abstract
Since Nichia announced their success in developing 2.5 cd blue (405nm) InGaN LED in October of 1995. This begins to cause enormous shock to the global photoelectric industry. Both the academia and industry are then actively involved in studying and developing this new technology. In the development of solid state lighting, near ultra-violet LED pump Red, Green and Blue phosphors that has the characteristic of wide optical spectrum range and higher color rendering. Therefore, the method of using blue LED to pump yellow phosphor will be replaced.
Due to the low internal efficiency of UV LED, we use mesh contact layer to replace the transparent contact layer in order to reduce the absorption of transparent contact layer and increase light extraction efficiency. This method can also increase the external quantum efficiency and output power, reduce the voltage of operation, improve current distribution. It could be to obtain good thermal stability and so on. In this paper, we fabricate the low resistivity of P-type contact and N-type contact. We apply the optimization to the chip process of LED. Optical and electrical properties of fabricated LEDs will also be discussed.
In the P-GaN contact, we use Ni/Au, ITO and Pd/Au as ohmic contact and measure the specific contact resistance. The specific contact resistance are , and for Ni/Au, ITO and Pd/Au, respectively. In the N-GaN contact, we use Cr/Pd/Au as ohmic contact and the specific contact resistance is . In the research of UV LED, we use traditional Ni/Au, ITO and mesh ITO structure as the transparent contact layer (TCL). Under 20 mA forward current injection, it was found that LED output power were 4.09 mW, 7.54 mW and 9.02 mW for Ni/Au TCL LED, ITO TCL LED and mesh ITO TCL LED, respectively. Based on this result, we found that GaN LED with Mesh TCL which can increase output power and better current spreading. Due to these characteristics, the mesh TCL structure could be applied to the big chip size LED. | en_US |