Green-Emitting $(lambda=525~{rm nm})$ InGaN/GaN Quantum Dot Light Emitting Diodes Grown on Quantum Dot Dislocation Filters

摘要

We have investigated the dislocation filtering characteristics of InGaN/GaN quantum dot multilayers grown at the substrate/active layer interface along the $c$-axis. Etch pit dislocation density measurements reveal a reduction in defect density by a factor of 5, from ${sim}{rm 5}times 10^{8}~{rm cm}^{-2}$ to ${sim}{rm 9.8}times 10^{7}~{rm cm}^{-2}$ in a GaN overlayer with an optimized quantum dot multilayer. This is accompanied by a reduction of electron and hole trap densities in the GaN layer by a factor of 3 and an increase in the luminescence efficiency of green-emitting ${rm In}_{rm 0.35}{rm Ga}_{0.65}{rm N}/{rm GaN}$ quantum dots grown atop such filters. Green-emitting $(lambda=525~{rm nm})$ quantum dot light emitting diodes having optimized dislocation filter show marked improvement in their current–voltage and light-current characteristics and in their external quantum efficiency. The peak efficiency is achieved at an injection level of 27 ${rm A}/{rm cm}^{2}$.