Annealing Impact on Emission of InAs Quantum Dots in GaAs/Al_0.30Ga_0.70As Structures with Different Capping Layers

The impact of annealing on the emission of InAs quantum dots (QDs) has been investigated in the GaAs/Al_0.30Ga_0.70As structures with different compositions of the quantum well (QW) layers covered of QDs: GaAs or Al_0.10Ga_0.75In_0.15As. The heat treatments of the QD structures were carried out at 640°C or 710°C for 2 h in an argon atmosphere. To estimate the compositions of QDs and capping QWs, photoluminescence (PL) and high-resolution X-ray diffraction have been applied. The QD structure with the Al_0.1Ga_0.75In_0.15As capping QWs has been characterized by a lower energy of the ground state emission (≈ 1.30 µm, 300°K), its highest intensity and the smaller full width at half maximum, compared to the QD structure with GaAs capping QWs. The extinction of the integrated PL intensity about 80 times was detected in the range 10–400 K for the QD structure with Al_0.10Ga_0.75In_0.15As capping compared to this extinction more than 1000 times detected in the QD structure with GaAs capping. The advantages obtained in the QD structure with Al_0.1Ga_0.75In_0.15As capping are attributed to the lower mismatch and stresses at the capping QW/InAs QD interfaces, as well as the higher chemical binding energy of the Al-As bonds, compared to their value for Ga-As, which decreases the interdiffusion efficiency of the Ga/In atoms.