Emission and HR-XRD study of MBE structures with InAs quantum dots and AlGaInAs strain reducing layers

Abstract GaAs/Al 0.30 Ga 0.70 As quantum wells (QWs) with InAs quantum dot (QD) arrays covered by the different capping layers: Al 0.30 Ga 0.70 As or Al 0.1 Ga 0.75 In 0.15 As, have been investigated by means of the photoluminescence (PL) and high resolution X-ray diffraction (HR-XRD) methods. It is revealed that the QD emission in the structure with Al 0.1 Ga 0.75 In 0.15 As capping is characterized by the lower PL energy, higher PL intensity of ground state emission and smaller its full width at half maximum (FWHM) in comparison with ground state QD emission at Al 0.30 Ga 0.70 As capping. The analysis of PL and HR-XRD scans has shown that the strain relaxation at high QW growth temperatures in the structure with Al 0.30 Ga 0.70 As capping was connected with changing significantly the material compositions of the QDs and capping layer. As a result the QD emission shifts into the higher energy range, the PL intensity decreases and the FWHMs of PL bands increase. In contrary, in the structure with Al 0.1 Ga 0.75 In 0.15 As capping the strain relaxation manifests itself by decreasing the InAs QD heights without changing the InAs QD material composition. The advantage of Al 0.1 Ga 0.75 In 0.15 As capping has been discussed.