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Electromodulated reflectance study of self-assembled Ge/Si quantum dots.

Yakimov A, Nikiforov A, Bloshkin A, Dvurechenskii A - Nanoscale Res Lett (2011)

Bottom Line: Up to three optical transitions are observed.The low-energy resonance is proposed to correspond to a band-to-continuum hole transition in the Ge valence band.The other two modulation signals are attributed to the spatially direct transitions between the electrons confined in the L and Δ(4) valleys of the Ge conduction band, and the localized hole states at the Γ point.

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Affiliation: Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia. yakimov@isp.nsc.ru.

ABSTRACT
We perform an electroreflectance spectroscopy of Ge/Si self-assembled quantum dots in the near-infrared and in the mid-infrared spectral range. Up to three optical transitions are observed. The low-energy resonance is proposed to correspond to a band-to-continuum hole transition in the Ge valence band. The other two modulation signals are attributed to the spatially direct transitions between the electrons confined in the L and Δ(4) valleys of the Ge conduction band, and the localized hole states at the Γ point.

No MeSH data available.


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The bias voltage dependence of the interband transition energy for peaks B and C. The solid curves are a fit to parabolic law.
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Figure 6: The bias voltage dependence of the interband transition energy for peaks B and C. The solid curves are a fit to parabolic law.

Mentions: The assignment of the high-energy electromodulation signals to the direct transitions is supported by analysis of the transition energies as a function of electric field. It is known that electric field applied perpendicular to quantum wells causes the shift of the electronic transition energy, the quantum-confined Stark effect (QCSE) [11]. Type-I systems, wherein the narrow-gap dot material presents a potential well for both electron and hole, exhibit a quadratic red-shift of the transition energy [7,11,12], while there should be a linear blue-shift of the spatially indirect transition for the systems with type-II band alignment [13,14]. In Figure 6, we plot the transition energies of peaks B and C as a function of applied reverse bias. As the bias increases, both peaks are red shifted by the QCSE, implying a type-I band-edge lineup.


Electromodulated reflectance study of self-assembled Ge/Si quantum dots.

Yakimov A, Nikiforov A, Bloshkin A, Dvurechenskii A - Nanoscale Res Lett (2011)

The bias voltage dependence of the interband transition energy for peaks B and C. The solid curves are a fit to parabolic law.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211264&req=5

Figure 6: The bias voltage dependence of the interband transition energy for peaks B and C. The solid curves are a fit to parabolic law.
Mentions: The assignment of the high-energy electromodulation signals to the direct transitions is supported by analysis of the transition energies as a function of electric field. It is known that electric field applied perpendicular to quantum wells causes the shift of the electronic transition energy, the quantum-confined Stark effect (QCSE) [11]. Type-I systems, wherein the narrow-gap dot material presents a potential well for both electron and hole, exhibit a quadratic red-shift of the transition energy [7,11,12], while there should be a linear blue-shift of the spatially indirect transition for the systems with type-II band alignment [13,14]. In Figure 6, we plot the transition energies of peaks B and C as a function of applied reverse bias. As the bias increases, both peaks are red shifted by the QCSE, implying a type-I band-edge lineup.

Bottom Line: Up to three optical transitions are observed.The low-energy resonance is proposed to correspond to a band-to-continuum hole transition in the Ge valence band.The other two modulation signals are attributed to the spatially direct transitions between the electrons confined in the L and Δ(4) valleys of the Ge conduction band, and the localized hole states at the Γ point.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia. yakimov@isp.nsc.ru.

ABSTRACT
We perform an electroreflectance spectroscopy of Ge/Si self-assembled quantum dots in the near-infrared and in the mid-infrared spectral range. Up to three optical transitions are observed. The low-energy resonance is proposed to correspond to a band-to-continuum hole transition in the Ge valence band. The other two modulation signals are attributed to the spatially direct transitions between the electrons confined in the L and Δ(4) valleys of the Ge conduction band, and the localized hole states at the Γ point.

No MeSH data available.


Related in: MedlinePlus