Effect of heavy ion implantation on self-assembled single layer InAs/GaAs quantum dots.

We report the degradation in photoluminescence efficiency of GaAs/(InAs/GaAs) quantum dot (QD) heterostructures subjected to 20 to 50 keV sulfur implantation. Sulfur ions of fluence ranging from 2.5 x 1013 to 2 x 1015 ions cm[?]2 were used for implantation. Implantation resulted in shift in photoluminescence emission towards lower wavelength and degradation in photoluminescence efficiency. X-ray diffraction analysis revealed reduction in crystalline quality of GaAs cap layer and an amorphous layer was accomplished with 50 keV sulfur implantation, with a fluence of 2.5 x 1014 ions cm[?]2. The amorphous layer was formed due to the overlap of defect clusters created during implantation, as a result of exceeding the critical nuclear energy density deposited in the GaAs system. Cross-sectional transmission electron microscopy revealed damage zones in the cap layer and deformation of QDs upon 50 keV sulfur implantation. Creation of damaged/amorphous GaAs layer probably increased the compressive strain in InAs/GaAs QDs, which resulted in change in energy gap of QDs and blue shift in photoluminescence emission. Implantation resulted in decrease in activation energy from 111 meV (20 keV) to 10 meV (50 keV S). Increase in implantation energy created defects/damage profile at a depth in the vicinity of the QDs. Non-radiative recombination of carriers through these defects might be the possible reason for the degradation of photoluminescence efficiency. [ABSTRACT FROM AUTHOR]