Controllability of the subband occupation of InAs quantum dots on a delta-doped GaAsSb barrier

Optical properties of InAs quantum dots (QDs) embedded in GaAsSb barriers with delta-doping levels equivalent to 0, 2, 4, and 6 electrons per dot (e/dot) are studied using time-integrated photoluminescence (PL).When the PL excitation power is increased the full width at half maximum (FWHM) of the 4 and 6 e/dot samples is found to increase at a much greater rate than the FWHMs for the 0 and 2 e/dot samples. PL spectra of the 4 e/dot sample show a high energy peak attributed to emission from the first excited states of the QDs, a result deduced to be due to preoccupation of states by electrons supplied by the delta-doping plane. When temperature dependent PL results are fitted using an Arrhenius function, the thermal activation energies for the 4 and 6 e/dot samples are similar and greater than the thermal activation energies for the 0 and 2 e/dot samples (which are similar to each other). This increased thermal activation energy is attributed to the enhanced Coulombic interaction in the InAs QD area by the delta-doping plane for higher doping levels. It is concluded that delta-doping of the barrier in QD systems is a feasible method for controlling the level of carrier occupation in a QD mediated intermediate band.