Light extraction efficiency (LEE) in AlGaN deep-ultraviolet (DUV) light-emitting diodes (LEDs) is investigated using finite-difference time-domain simulations. For flip-chip and vertical LED structures, LEE is obtained to be <10% due to strong DUV light absorption in the p-GaN layer. In flipchip LEDs, LEE of transverse-magnetic (TM) modes is found to be more than ten times smaller than that of transverse-electric (TE) modes, which explains the decreasing behavior of external quantum efficiency of DUV LEDs with decreasing wavelength. It is also found that vertical LED structures can have advantages over flip-chip structures for increasing LEE in the TM mode. #

Dominant nonradiative recombination mechanisms as a function of nonradiative current were investigated in InGaN blue light-emitting diodes (LEDs). Each radiative and nonradiative current components were separated from the total current by using the information of the internal quantum efficiency (IQE), obtained from the temperature-dependent electroluminescence measurement. By analyzing voltage and light output power as functions of nonradiative current, we were able to understand that the dominant nonradiative mechanisms of the LEDs vary with the competing mechanisms of Shockley-Read-Hall or tunneling recombination at low current density to the carrier overflow at high current density, inducing the IQE droop. #

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