Electroluminescence analysis of 1.3‐1.5 μm InAs quantum dot LEDs with (Ga,In)(N,As) capping layers

Abstract

AbstractThe electroluminescence (EL) of a series of InAs/(Ga,In)(N,As) self‐assembled quantum dot light emitting diodes (QDLEDs) with different capping layer composition is analysed. Room temperature EL close to 1.5 μm is demonstrated using 15% In and 2% N in the capping layer. The origin of the different peaks present in the EL spectra of N‐containing devices has been studied and the higher energy peaks have been attributed to emission from the quantum well constituted by the wetting and the capping layers. The effect of rapid thermal annealing (RTA) on the EL is analysed. It is found that the EL emission energy blue‐shifts after RTA. This blue‐shift is smaller for the N‐containing devices (∼40 meV) than for a InAs/In0.15Ga0.85As reference QDLED (∼85 meV). In addition, the QDLEDs power slope efficiency is also studied at 14 K. It is readily seen that this efficiency decreases by three orders of magnitude with the addition of 2% N to the InGaAs capping layer. Nevertheless, after RTA, this efficiency recovers partially, increasing by two orders of magnitude and reaching values close to those of the N‐free reference QDLEDs. This enhancement can be explained by the reduction of the non‐radiative recombination centre density in the capping layer after RTA, which leads to a higher carrier injection efficiency into the QDs. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)