Optical Properties and HR-XRD Study of /InGaAs/Al Ga As/GaAs Structures with InAs Quantum Dots and Different Capping Layers

Abstract

The Al0.30Ga0.70As /InGaAs/AlGaInAs/ Al0.30Ga0.70As structures with embedded InAs quantum dots (QDs) covered by strain reduced AlGaInAs capping layers have been investigated in an as-grown state using the photoluminescence (PL) and high resolution X ray diffraction (HR-XRD) methods. Two types of QD structures with different quantum well (QW) capping layers: Al0.10In0.15Ga0.75As (#1) and Al0.40In0.15Ga0.45As (#2), and buffer QW layers: In0.15Ga0.85As (#1) and In0.25Ga0.75As (#2) are compared. It is revealed that QD emission in the structure with Al0.10In0.15Ga0.75As capping (#1) is characterized by the higher PL intensity of the ground state (GS) band and smaller the full with at half maximum (FWHM), compared to those in #2. The variation of the GS emission intensity versus temperature has been monitored within the range of 10-500K. It was revealed more significant PL thermal quenching in #1 compared with #2. HR-XRD study has shown that the both QD structures are characterized by the best quality of the QW interfaces with the high numbers of Pendellösung peaks. The analysis of HR-XRD scans permits to estimate the values of the elastic strains in the studied QD structures, which were higher in #2 compared with #1. The peculiarities of PL spectra and HR-XRD are analyzed and the advances of studied QD structures have been compared and discussed.