AlGaInAs capping layer impact on emission and structure of AlGaAs/GaAs quantum wells with InAs quantum dots

Three types of GaAs/Al(0.30)Gao(0.70) As quantum wells (QWs) with InAs quantum dots (QDs) cavered by the different capping layers: GaAs (#1), Al0.30Ga0.70As (#2) and Al(0.1)Gao(0.75)In(0.15)As (#3), have been investigated. The photoluminescence (PL), its temperature dependence and high resolution X-ray diffraction (HR-XRD) methods were applied. It is revealed that QD emission in the structure #3 is characterized by the lower PL peak energy, highest PL intensity and smaller half widths of PL bands, in comparison with the QD emissions in #1 and #2. PL temperature dependences have been studied that revealing the QD material composition in #3 is closer to InAs than those in #1 and #2. HR-XRD scan fitting permits to understand the process of strain relaxation in studied structures at high QW growth temperatures. This process in the structures #1 and #2 was connected with material composition varying the QDs and capping layers due to Ga/In atom intermixing that leads to the QD emission shift into the higher energy range and PL intensity decreasing. Meanwhile in the structure #3 with Al0.1Ga0.75In0.75As capping, the strain relaxation manifests itself by InAs QD height decreasing without changing the InAs QD material composition. The advantages of Al0.1Ga0.75In0.15As capping layer used and its impact on the emission of InAs QDs have been discussed.