Date

Place

Room C (Room 323)
10. LEDs and Lighting II
August 19, 2015 (Wednesday)
14:00 ~ 15:30

[10-1]
14:00 ~ 14:25
Title:[Invited] Enhancement in Light-Extraction Efficiency of Deep Ultraviolet Light-Emitting Diodes by Utilizing Transverse-Magnetic-Dominant Emission
Jong Won Lee, Dong Yeong Kim, Jun Hyuk Park (POSTECH, Korea), Jungsub Kim, Yong-Il Kim, Youngsoo Park (Samsung Electronics Co., Ltd., Korea), E. Fred Schubert (Rensselaer Polytechnic Inst., U.S.A.), and Jong Kyu Kim (POSTECH, Korea)
Abstract: We propose a new type of LEE-enhancing method for AlGaN-based DUV LEDs by utilizing its strong side emission, called sidewall-emission-enhanced (SEE) DUV LEDs. The proposed SEE DUV LEDs include multiple narrow active-region mesa stripes with Al-based reflectors to extract the strong TM-polarized sidewall emission and to reflect UV photons, either up to the free space by Al-on-regrown-GaN reflector (top-emitting SEE DUV LEDs) or down to the free space by MgF2/Al omnidirectional reflector on inclined surface of trapezoidal active mesa stripes (bottom-emitting SEE DUV LEDs). We experimentally observed that the light output power increases upon increasing the active-region sidewall perimeter, which is elucidated by the strong sidewall emission of the AlGaN active layer with high Al content. The effect of enhanced sidewall emission and the DUV reflection by the Al coated reflectors is analyzed by using finite element method and analytical modeling. Finally, strategies to further enhance the LEE up to the theoretical optimum value and control emission directionality are discussed.
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