Internal quantum efficiency (IQE) of InGaN/GaN UV LEDs with patterned sapphire substrates (PSS) was investigated using electroluminescence (EL) and photoluminescence (PL) methods. The physical mechanisms that affect temperature-dependent EL efficiency as a function of injected carrier density were deduced. In order to reduce the density of non-radiative recombination centers to improve quantum efficiency, improvement of crystal quality and reduction in the number of defects are necessary. PSS LEDs showed better EL characteristics than non-PSS LEDs because of the improved epitaxial quality. Contrary to PL IQE, EL IQE was significantly affected by carrier injection efficiency, especially at low temperature when high bias voltage was applied to the p-n junction. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.