INSTITUTE OF PHYSICS PUBLISHING SEMICONDUCTOR SCIENCE AND TECHNOLOGY Semicond. Sci. Technol. 21 (2006) 184–189 doi:10.1088/0268-1242/21/2/016 High brightness AlGaInP-based light emitting diodes by adopting the stripe-patterned omni-directional reflector Y J Lee 1,2 , T C Lu 1 , H C Kuo 1 , S C Wang 1 , M J Liou 2 , C W Chang 2 , T C Hsu 2 , M H Hsieh 2 , M J Jou 2 and B J Lee 2 1 Department of Photonic and Institute of Electro-Optical Engineering, National Chiao Tung University, 1001 TaHsueh Road, Hinchu 300, Taiwan, Republic of China 2 R&D Division, Epistar Co., Ltd, Science-based Industrial Park, Hsinchu 300, Taiwan, Republic of China Received 19 October 2005, in final form 7 December 2005 Published 12 January 2006 Online at stacks.iop.org/SST/21/184 Abstract An n-side-up AlGaInP-based LED operating at a wavelength of 630 nm with a stripe-patterned omni-directional reflector (ODR) was fabricated by adopting the adhesive-layer bonding scheme. It is demonstrated that the periodic and geometrical shape of the stripe-patterned array improves the light extraction efficiency by increasing the extraction of guided light. Compared to the conventional ODR LED, the stripe-patterned ODR LED significantly enhanced the output power and with only a slightly higher forward voltage. This improvement was analysed by the scanning near-field optical microscope (SNOM) and the optimized dimension of stripe patterns was also calculated on the basis of a Monte Carlo ray tracing simulation. According to the above analysis, the increase of light extraction could not only be attributed to the geometrical shape of the stripe patterns that redirect the trapped light towards the top-escaping cone of the LED surface but also to the repetitive stripe-patterned array of diffracting elements that effectively diffract the guided light outside the LED surface. Moreover, the optimized dimension of the stripe pattern is 3 μm wide, 2 μm deep and spaced 3 μm apart, which coincides with experimental results. (Some figures in this article are in colour only in the electronic version) Introduction For the yellow-to-red spectral region, the quaternary AlGaInP material system, grown by low-pressure metal-organic chemical vapour deposition (MOCVD), has proven to be the best choice in many applications such as interior and exterior automotive lighting, traffic lights, full colour displays, and all kinds of indoor and outdoor signs [1, 2]. A new level of high light efficiency was achieved over this spectral regime. Due to the intense investigation of previous studies, the epitaxial technology of AlGaInP materials was quite mature, and as a consequence, around 100% internal quantum efficiency was achieved [3]. However, the quaternary AlGaInP LEDs suffer poor light extraction efficiency due to the total internal reflection of light between air (epoxy) and the semiconductor. Approximately 1/(4n 2 ) of the light from the active region can escape from the top and bottom of the device, where n denotes the refractive index of semiconductor materials [4]. Furthermore, the AlGaInP LEDs are grown on GaAs substrates that are opaque for the emitting wavelengths of this quaternary material. Hence, most of the light radiated from the active region is trapped in the device and is eventually absorbed by the GaAs absorbing substrate. Thus, the major issue was then how to get the photons that had been generated 0268-1242/06/020184+06$30.00 © 2006 IOP Publishing Ltd Printed in the UK 184