Exciton radiative lifetime in sub-monlayer and stranskii-Krastanow grown InGaAs/GaAs quantum dots

Publication: Research - peer-reviewConference abstract for conference – Annual report year: 2008

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Submonolayer (SML) growth of quantum dots (QDs) presents an alternative approach to Stranskii-Krastanow (SK) grown QDs [1-3]. SML growth has been applied to fabricate QD-based high-power edge-emitting lasers [1] as well as single-mode vertical-cavity surface-emitting lasers with high modulation bandwidth [3]. The superior performance of SML QD lasers has usually been attributed to the high density and uniformity of SML QDs [2]. However, another important parameter governing the maximum modal gain from optical transitions in QDs is the oscillator strength, inversely proportional to the exciton radiative lifetime rad [4]. Here, we compare the exciton radiative lifetime of SML-grown and SK-grown InGaAs/GaAs QDs at 10 K, via time-resolved photoluminescence (PL). The SML-QDs, were formed by 10 cycles of alternate deposition of 0.5 monolayer (ML) InAs and 2.5 ML GaAs, at 500 °C. The SK-QDs were formed by depositing 4.1 ML In0.6Ga0.4As on GaAs. The PL spectra indicate that the SML-QDs show better uniformity than the SK-QDs. Transient PL for SML and SK QDs at 10 K, where the PL decay time d is dominated by the exciton radiative lifetime, show d = 90 ps for SML-QDs which is much shorter than for SK-QDs (d = 600 ps). By a detailed analysis of the temperature dependence we find that the radiative lifetime rad of SML-QDs is short (90 ps) and almost independent of temperature below 50K and increase to about 800 ps at room temperature [5]. The short exciton radiative lifetime of SML-QDs could be one of the key reasons for the observed high performance of the SML QD lasers.
Original languageEnglish
Publication date2008


Conference15th International COnferecne on Superlattices, Nanostructures and Nanodevices
CityNatal, Brazil
Period01/01/08 → …
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ID: 3066318