Light emitting diodes with InAs/GaAsSb self-assembled quantum dot layer embedded in GaAs

Abstract

Luminescence properties of metalorganic vapor phase epitaxy grown light emitting diodes (LEDs) with active InAs/GaAs quantum dot (QD) layer covered by GaAsSb strain reducing layer (SRL) were investigated at temperatures from 10 to 400K. Results show that the use of GaAsSb SRL with up to 14% Sb strongly increases luminescence, redshifts the emission maximum up to 1.4μm while keeping the type I transition, narrows the luminescence linewidth and keeps the separation energy between the ground and excited state as in InAs/GaAs QD LEDs without SRL. The strong ground state emission which persists up to 400K is dominated by recombination of electrons and holes confined in QDs while the broad emission from excited states, which dominates below 250K, involves recombination from the states located in QDs and SRL. The ground state electroluminescence shows the typical Stranski–Krastanov dot temperature properties: the thermally induced narrowing of the electroluminescence linewidth and the increased QD gap energy shrinkage with temperature. The electroluminescence intensity of the ground and excited state transitions increases with temperature (up to 80K) due to the thermal escape of electrons from the wetting layer which reduces radiative recombination via wetting layer states. The dominant mechanism responsible for the thermal quenching of electroluminescence at elevated temperatures is the escape of electrons from QDs to the GaAs barrier.