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Spin effects in InAs self-assembled quantum dots.

Dos Santos EC, Gobato YG, Brasil MJ, Taylor DA, Henini M - Nanoscale Res Lett (2011)

Bottom Line: We have studied the polarized resolved photoluminescence in an n-type resonant tunneling diode (RTD) of GaAs/AlGaAs which incorporates a layer of InAs self-assembled quantum dots (QDs) in the center of a GaAs quantum well (QW).We have observed that the QD circular polarization degree depends on applied voltage and light intensity.Our results are explained in terms of the tunneling of minority carriers into the QW, carrier capture by InAs QDs and bias-controlled density of holes in the QW.

View Article: PubMed Central - HTML - PubMed

Affiliation: Physics Department, Federal University of São Carlos, São Carlos, Brazil. yara@df.ufscar.br.

ABSTRACT
We have studied the polarized resolved photoluminescence in an n-type resonant tunneling diode (RTD) of GaAs/AlGaAs which incorporates a layer of InAs self-assembled quantum dots (QDs) in the center of a GaAs quantum well (QW). We have observed that the QD circular polarization degree depends on applied voltage and light intensity. Our results are explained in terms of the tunneling of minority carriers into the QW, carrier capture by InAs QDs and bias-controlled density of holes in the QW.

No MeSH data available.


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Typical PL spectrum obtained and voltage dependence of PL intensity. (a) Typical PL spectrum and (b) PL integrated intensity as a function of applied voltage at 2 K, for B = 0 T and 10-mW laser excitation.
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Figure 3: Typical PL spectrum obtained and voltage dependence of PL intensity. (a) Typical PL spectrum and (b) PL integrated intensity as a function of applied voltage at 2 K, for B = 0 T and 10-mW laser excitation.

Mentions: Figure 3a shows a typical PL spectrum obtained under zero magnetic field (B = 0 T). The GaAs contact layers show two emission bands: the free-exciton transition from the undoped space-layer and the recombination between photogenerated holes and donor electrons from the n-doped GaAs layers. The QD emission is observed at about 1.25 eV and show lower PL intensity. We do not observe any emission from wetting layer because carriers preferentially recombine in lower energy states in QDs. We have also observed that the QD PL intensity depends strongly on the applied voltage at the region of low bias. We have observed a clear correlation between the I(V) curve and QD PL intensity (Figure 3b). Under applied bias, tunneling carriers can be promptly captured by QDs and then recombine radiatively. As explained before, due to this fast carrier capture process, the QD luminescence is sensitive to the resonant tunneling of carriers through the QW levels. Figure 3b also shows the voltage dependence of PL intensity from GaAs contact layer emission. Remark that QD and contact emission are in anti-phase with each other. The observed reduction of contact emission and increase of QD emission in low bias can be explained by the reduction of holes recombining in GaAs contact layer due to the efficient capture into the QDs [8,9].


Spin effects in InAs self-assembled quantum dots.

Dos Santos EC, Gobato YG, Brasil MJ, Taylor DA, Henini M - Nanoscale Res Lett (2011)

Typical PL spectrum obtained and voltage dependence of PL intensity. (a) Typical PL spectrum and (b) PL integrated intensity as a function of applied voltage at 2 K, for B = 0 T and 10-mW laser excitation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211160&req=5

Figure 3: Typical PL spectrum obtained and voltage dependence of PL intensity. (a) Typical PL spectrum and (b) PL integrated intensity as a function of applied voltage at 2 K, for B = 0 T and 10-mW laser excitation.
Mentions: Figure 3a shows a typical PL spectrum obtained under zero magnetic field (B = 0 T). The GaAs contact layers show two emission bands: the free-exciton transition from the undoped space-layer and the recombination between photogenerated holes and donor electrons from the n-doped GaAs layers. The QD emission is observed at about 1.25 eV and show lower PL intensity. We do not observe any emission from wetting layer because carriers preferentially recombine in lower energy states in QDs. We have also observed that the QD PL intensity depends strongly on the applied voltage at the region of low bias. We have observed a clear correlation between the I(V) curve and QD PL intensity (Figure 3b). Under applied bias, tunneling carriers can be promptly captured by QDs and then recombine radiatively. As explained before, due to this fast carrier capture process, the QD luminescence is sensitive to the resonant tunneling of carriers through the QW levels. Figure 3b also shows the voltage dependence of PL intensity from GaAs contact layer emission. Remark that QD and contact emission are in anti-phase with each other. The observed reduction of contact emission and increase of QD emission in low bias can be explained by the reduction of holes recombining in GaAs contact layer due to the efficient capture into the QDs [8,9].

Bottom Line: We have studied the polarized resolved photoluminescence in an n-type resonant tunneling diode (RTD) of GaAs/AlGaAs which incorporates a layer of InAs self-assembled quantum dots (QDs) in the center of a GaAs quantum well (QW).We have observed that the QD circular polarization degree depends on applied voltage and light intensity.Our results are explained in terms of the tunneling of minority carriers into the QW, carrier capture by InAs QDs and bias-controlled density of holes in the QW.

View Article: PubMed Central - HTML - PubMed

Affiliation: Physics Department, Federal University of São Carlos, São Carlos, Brazil. yara@df.ufscar.br.

ABSTRACT
We have studied the polarized resolved photoluminescence in an n-type resonant tunneling diode (RTD) of GaAs/AlGaAs which incorporates a layer of InAs self-assembled quantum dots (QDs) in the center of a GaAs quantum well (QW). We have observed that the QD circular polarization degree depends on applied voltage and light intensity. Our results are explained in terms of the tunneling of minority carriers into the QW, carrier capture by InAs QDs and bias-controlled density of holes in the QW.

No MeSH data available.


Related in: MedlinePlus