Optical and electronic properties of GaAs-based structures with columnar quantum dots

Photoreflectance spectroscopy and photoluminescence have been used to study the optical properties and electronic structure of InGaAs quantum rods grown by molecular beam epitaxy. Spectral features associated with interband optical transitions localized in the quantum rod and the surrounding quantum well regions are examined. Experimental results are compared with calculations performed within the envelope function approximation. A red shift of the quantum rod-and a blue shift of the quantum well-related optical transitions, along with a significant increase in PL intensity have been observed if an As4 source is used instead of an As2 source during the molecular beam epitaxial growth.

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“…The later assignment is supported by PL data (Fig. 1), as well as by contactless electroreflectance (CER) spectroscopy [7].…”

Section: Resultssupporting

confidence: 52%

Photoreflectance of Epitaxial InGaAs Quantum Rods

et al. 2011

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“…9) of a columnar QD having y = 1.8 MLs, N = 10 and x = 0.7 for 17 mW (dashed line) and 50 mW (solid) pump power shows several peaks in the 1,000-1,100 nm wavelength region, which can be attributed to several states in the QDs. The state-filling behavior observed for different pump powers along with previous detailed characterization and modeling (Motyka et al 2007) allows us to evidence emissions from the 2D QW, excited-(ES) and ground-state (GS). Based on this active material, SOA structures were grown and processed, incorporating five layers of columnar QDs obtained by depositing 1.8 MLs InAs seed layer and then 10 or 18 cycles of 3 ML GaAs/0.62 ML InAs.…”

Section: Columnar Quantum Dotsmentioning

confidence: 99%

Polarization dependence of electroluminescence from closely-stacked and columnar quantum dots

Ridha

Rossetti

et al. 2008

Opt Quant Electron

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Quantum dots (QDs) have a potential for application in semiconductor optical amplifiers (SOAs), due to their high saturation power related to the low differential gain, fast gain recovery and wide gain spectrum compared to quantum wells. Besides all advantages, QDs realized by Stranski-Krastanov growth mode have a flat shape which leads to a gain anisotropy and a related transverse magnetic (TM) and -electric (TE) polarization dependence as compared to bulk material. This has so far prevented their applications in SOAs. It has been suggested that control of optical polarization anisotropy of the QD can be obtained through QD shape engineering, in closely stacked or columnar QDs (CQDs). To this aim, we have fabricated and tested SOA structures based on closely-stacked and columnar QDs. Closely-stacked InAs QDs with 4, 6 and 10 nm GaAs spacer showed a minor improvement in the ratio of TM and TE integrated electroluminescence (EL) over standard QDs along with a strong reduction in efficiency. In contrast, a large improvement was obtained in CQDs, depending on the number of stacked submonolayers which can be attributed to the more symmetric shape of columnar QDs. A relatively small spectral separation ( E ∼ 21 meV) between TE-and TM-EL peaks has been observed showing that heavy-and light hole-like states, respectively are energetically close in these QDs. These results indicate that columnar QDs have a significant potential for polarization-independent QD SOA.

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“…odulation spectroscopy 1,2) i.e., photoreflectance (PR) in its standard dispersive mode, has been proven as a very powerful tool for investigating the optical properties of semiconductor structures like quantum well, quantum dot, or quantum dash systems. [3][4][5][6] Due to its high sensitivity to optical transitions, it has been successfully used for the investigation and characterization of semiconductor-based structures dedicated for usual photonic applications in a broad spectral range from UV ($275 nm) 7) up to mid infrared (4 m). 8) Nevertheless, due to some fundamental limitations, it becomes difficult or even impossible to exploit modulation spectroscopy by means of a standard grating-based system significantly beyond 3 m, i.e., in the mid-and far-infrared regions.…”

mentioning

confidence: 99%

Fast Differential Reflectance Spectroscopy of Semiconductor Structures for Infrared Applications by Using Fourier Transform Spectrometer

Motyka

Misiewicz

2010

Appl. Phys. Express

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Fast differential reflectance (FDR) spectroscopy has been proposed as a form of photoreflectance (PR) measurement and employed for optical investigations of type I and II quantum well structures dedicated for laser applications in the mid infrared. Differential spectra with a high signal-to-noise ratio have been achieved within times of the order of a few seconds in the 1–4 µm spectral range. We have demonstrated that the FDR technique can be successfully exploited in the fast optical characterization and investigation of semiconductor-based complex systems in the long-wavelength spectral range with an optimistic projection into the far infrared.

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Optical and electronic properties of GaAs-based structures with columnar quantum dots

Cited by 13 publications

References 19 publications

Photoreflectance of Epitaxial InGaAs Quantum Rods

Photoreflectance of Epitaxial InGaAs Quantum Rods

Polarization dependence of electroluminescence from closely-stacked and columnar quantum dots

Fast Differential Reflectance Spectroscopy of Semiconductor Structures for Infrared Applications by Using Fourier Transform Spectrometer

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