Carrier escape mechanism in laterally correlated InAs sub-monolayer quantum dots using temperature dependent photoluminescence

Abstract We have quantitatively investigated relative effects of photo-carrier escape mechanism upon the quenching of photoluminescence with temperature in an ensemble of embedded InAs sub-monolayer (SML) quantum dots by varying InAs SML coverage from 0.4 ML to 0.8 ML. The mutual interplay of carrier recombination and tunneling throughout the laterally coupled quantum dots for different InAs coverage have been established to determine the temperature dependent photoluminescence (TDPL) spectra. The respective characteristic life times were extracted from the individual TDPL spectra by fitting with model carrier rate equation. The subsequent enhancement of inter-dot tunnel strength with respect to the carrier recombination rate with increasing InAs coverage has been marked out to be responsible for sustainable photoluminescence efficiency at higher temperature. Enhancement of tunneling rate with increasing InAs SML coverage has been physically described as consequence of reduced average inter-dot lateral separation as estimated from grazing incidence small angle x-ray scattering (GISAXS) measurement. Moreover, we have showed the anomalous decrease of spectral linewidth with temperature can also be described as a consequence of the tunnel induced faster inter-dot carrier transfer at higher sub-monolayer coverage. The fact that quantum dot wetting layer is absent in SML QD has resulted in speeding up the carrier transfer mechanism through inter-dot tunneling pathways with tunnel time as low as 350 ps which is significantly faster than that of 1328 ps found for reference conventional InAs/GaAs Stranski-Krastanov (SK) QDs.