Comprehensive study of InAs/GaAs quantum dots by means of complementary methods

Structural, optical, and electronic properties of self-organized InAs/GaAs quantum dots (QDs) were studied by means of atomic force microscopy (AFM), photoluminescence measurements (PL), and deep level transient spectroscopy (DLTS). We found that a well defined group of QDs with low size dispersion as revealed by AFM maintains its properties in PL spectra even if the QDs are covered by GaAs. Two well separated emission lines attributed to the QD-related ground- and excited-state transitions, respectively are found in the PL spectra. Contrary to the optical picture of a characteristic simplicity, DLTS spectra are found with higher complexity. This is due to combined thermal/tunneling processes and multi-particle emission. Despite the relatively good understanding of optical and electrical properties of QDs in PL and DLTS, respectively, there are still discrepancies between electrical and optical data for the energy of the QD ground states, which need more investigations to be explained.