The influence of strain on the optical emission from defect-enhanced Ge/Si quantum dots
Sprache des Vortragstitels:
E-MRS Fall Meeting
Sprache des Tagungstitel:
Defect-enhanced quantum dots are all-group-IV room-temperature light-sources consisting of epitaxial Ge/Si quantum dots (QDs) and extended point defects that are intentionally introduced upon low energy ion implantation. Both carrier types, electrons and holes, are confined within the QD region, i.e. holes experience quantum confinement due to the large band offsets between Si and Ge, while electrons are trapped by introduced defects of split- self-interstitial structure. The most prominent features of DEQDs are clear signs for optically-pumped lasing, absence of thermal quenching of the photoluminescence emission up to room-temperature, and the demonstration of LEDs, grown directly on Si working efficiently up to 100°C. Here, we present in a combined experimental and theoretical approach that the ~3.5% biaxially compressively strained Ge on Si ?hut-cluster? QDs used up to now seem to be all but ideal host matrices for the light-emitting defects in DEQDs. Theoretical calculations based on density functional theory suggest that reducing the amount of compressive strain in the QD leads to a strong enhancement of the oscillator strength of the radiative transitions in this interlaced defect-QD system. Experimental evidence for improved photoluminescence emission for less-strained DEQD-systems as well as means to arbitrarily strain the DEQDs using thin DEQD membranes on piezoelectric actuators will be presented. These findings can be the key to tap the full potential of DEQD light-sources for applications in the field of Si photonics and beyond.