Enhancement in emission angle of the blue LED chip fabricated on lens patterned sapphire (0 0 0 1)

Blue light-emitting diodes (LEDs) with an InGaN multi-quantum-well (MQW) structure were fabricated on a lens patterned sapphire substrate (LPSS) using a single growth process of metalorganic chemical vapor deposition (MOCVD). In the present study, the PSS with lens shape along the 〈0 0 0 1〉sapphire direction was fabricated by inductively coupled plasma (ICP) dry etching method. When the blue LED device was operated at a forward-bias current of 20 mA at room temperature, the output power and the luminous intensity were estimated to be 69.3 μW and 159.2 mcd respectively. It was found that the luminous intensity of LPSS–LED was 2.5 times higher than that of the conventional sapphire substrate LED at an injection current of 20 mA. At 20 mA injection current the emission angle of LPSS–LED was 161.46° which is 1.17 times higher than that of CSS–LED. More importantly the LED on LPSS demonstrates a higher output power and an enhancement of the emission efficiency compared to that of LED on conventional sapphire substrate (CSS). In addition, the reduction of full width at half maximum in the HR-XRD curves of GaN on PSS suggested improved crystal quality.