Improving output power performance of InGaN-based light-emitting diodes by employing step-down indium contents

Abstract

We investigated the effect of step-down indium content in InGaN quantum wells (QWs) on the output efficiency of fully packaged InGaN-based light-emitting diodes (LEDs). Both the reference and step-down LED chips give maximum external quantum efficiencies (EQE) of 54.65 and 54.99% at a current density of 4.17A/cm(2), respectively. Step-down LEDs show a lower efficiency droop than reference LEDs. The step-down LEDs exhibit a 5.3% higher EQE at 83.3 A/cm(2) than the reference LEDs. As the current density increases from 1.39 to 9.03A/cm(2), the electroluminescence (EL) intensity peaks of the step-down LEDs are slightly more shifted towards the larger energy side than those of the reference LEDs. The polarization field is estimated to be 1.34 and 1.41 MV/cm for the reference and step-down LEDS, respectively. The simulated internal quantum efficiency results of the reference and step-down LEDs are in agreement with the experimental results. The simulation results show that the step-down LEDs have higher hole injection efficiency than the reference LEDs. On the basis of the simulation results, the blue-shift behavior of the reference and step-down LEDs is described and discussed. (c) 2015 The Japan Society of Applied Physics