Anomalous temperature behavior of the excitonic emission of a 3 ML ultra-thin quantum well of CdSe

Alfaro‐Martínez, Adrián; Hernández‐Calderón, I.

doi:10.1016/j.mejo.2005.02.128

Cited by 4 publications

(2 citation statements)

References 11 publications

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“…These fluctuations can be identified by means of PL spectroscopy by the S‐shaped evolution of the excitonic peak energy as a function of temperature, effect that is related to exciton migration between regions with different Cd content. [ 16 ] At RT the exciton migration favors the exciton localization in regions of lower Cd content; then, after the consideration of the calculations presented in Figure 1 and considering possible migration effects, as will be discussed later, we need to assure that we can have a Cd nominal concentration in the QW of at least ≈65%. It is important to note that such QW layer would result in a lattice mismatch of at least 4.6% with the ZnSe barriers.…”

Section: Quantum Well Featuresmentioning

confidence: 99%

Room‐Temperature Yellow Emission of a High Cd Content (x = 0.70), Highly Strained, Layer‐by‐Layer Grown Zn_1−xCd_xSe/ZnSe Quantum Well

Villa-Martínez

Šutara

Hernández‐Calderón

2022

Physica Status Solidi (b)

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The results of the growth and characterization of an 8 monolayers (MLs) thick Zn1−xCdxSe/ZnSe quantum well (QW) with quite high Cd content (x = 0.70) are presented. At room temperature (RT), the QW presents yellow excitonic emission at 2.179 eV (569 nm, same color as the yellow line of a Kr ion laser). Despite the large Cd content, the RT photoluminescence spectrum shows a well‐defined, symmetric excitonic peak with relatively narrow full width at half maximum, indicating a good structural quality of the QW that is attributed to the sequential layer‐by‐layer growth mode achieved by the use of the submonolayer pulsed beam epitaxy (SPBE) technique. The ZnSe barriers are grown by molecular beam epitaxy (MBE); the QW heterostructure is deposited on top of a GaAs(001) substrate at 275 °C. Scanning transmission electron microscopy indicates a homogeneous smooth QW layer. The evolution of the excitonic emission energy with increasing temperature in the 19–300 K range shows the well‐known S‐shaped behavior that is interpreted in terms of exciton migration.

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Section: Quantum Well Featuresmentioning

confidence: 99%

Room‐Temperature Yellow Emission of a High Cd Content (x = 0.70), Highly Strained, Layer‐by‐Layer Grown Zn_1−xCd_xSe/ZnSe Quantum Well

Villa-Martínez

Šutara

Hernández‐Calderón

2022

Physica Status Solidi (b)

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High Resolution Investigation on the Structure of Quantum Wells in the System CdSe-ZnSe

Calderón¹,

Hernández‐Calderón

2011

Microsc Microanal

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The excitonic emission of ultra-thin quantum wells (1 to 4 monolayers, ML) can be tuned from the yellow-green to the blue spectral range [1]. Therefore they are of interest for the fabrication of light emitting devices. CdSe and ZnSe have similar crystalline structures (fcc, zinc blende) and differ in the lattice parameter a (a is 0.567 and 0.608 nm for ZnSe and CdSe, respectively). There is therefore a strong lattice mismatch leading to strained interfaces when the QW is sufficiently thin (1 to 3 ML) and generation of defects above 4 ML of thickness. In this respect one monolayer is the thickness of a cationanion layer and it is given by a/2. Thick QWs (above 4 ML) have broad and weak emission which is inappropriate for application as light emitting devices. Thus the knowledge of their structure and composition is of prime importance becoming the objective of this investigation with localized microscopy techniques. Previous efforts have concentrated on non-localized characterization techniques such as photoluminescence. Electron microscopes in high resolution modes have been utilized at 300 and 200 kV both in TEM and STEM mode and with the use of aberration correctors. Samples have been prepared by conventional cross section techniques to ensure the highest possible resolution. Figure 1 shows STEM images of quantum wells in a nominally 15 ML thick QW. The Cd rich QW can be identified both in low magnification (Fig. 1a) and in the high resolution images shown in Figs. 1b,c. The sample orientation [011] allows imaging of dumbbells characteristic of this structure. The Z contrast is clear enough to determine the QW thickness as 15 ML in average. There is however some distortion and slight overall bending of the QW, most likely due to the sample thinning. The composition is rather homogeneous although with larger variations on the deposit side since Zn atoms can substitute for Cd atoms during epitaxial growth. Figure 2 shows STEM images of a QW nominally 3 ML thick. The thickness is around 3ML but the last layer (following the deposit direction) is slightly inhomogeneous. In this thin QWs, it is possible to find deviations from the planarity of the deposits. However they are rather small and most likely mimic the surface of the supporting surface. Additionally there is a small thickness variation that most likely arises from the involved projection along the selected observation direction, too. Direct measurement of chemical composition has been done by using energy loss spectroscopy (EELS). These results support the above conclusions. Transmission electron microscopy with exit wave reconstruction allows imaging of these beam sensitive materials with a slightly better precision and in a shorter time as STEM methods but with a reduction of contrast. Figure 3 shows an example with a direct TEM image. It shows strain contrast (which can be reduced in the EWR procedure) and low contrast. However the QW position and thickness can always be precisely found by measuring the intensity profile (Fig 3b) where a characteristi...

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Epitaxial growth of thin films and quantum structures of II–VI visible-bandgap semiconductors

Hernández‐Calderón

2013

Molecular Beam Epitaxy

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Anomalous temperature behavior of the excitonic emission of a 3 ML ultra-thin quantum well of CdSe

Cited by 4 publications

References 11 publications

Room‐Temperature Yellow Emission of a High Cd Content (x = 0.70), Highly Strained, Layer‐by‐Layer Grown Zn_1−xCd_xSe/ZnSe Quantum Well

Room‐Temperature Yellow Emission of a High Cd Content (x = 0.70), Highly Strained, Layer‐by‐Layer Grown Zn_1−xCd_xSe/ZnSe Quantum Well

High Resolution Investigation on the Structure of Quantum Wells in the System CdSe-ZnSe

Epitaxial growth of thin films and quantum structures of II–VI visible-bandgap semiconductors

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Anomalous temperature behavior of the excitonic emission of a 3 ML ultra-thin quantum well of CdSe

Cited by 4 publications

References 11 publications

Room‐Temperature Yellow Emission of a High Cd Content (x = 0.70), Highly Strained, Layer‐by‐Layer Grown Zn1−xCdxSe/ZnSe Quantum Well

Room‐Temperature Yellow Emission of a High Cd Content (x = 0.70), Highly Strained, Layer‐by‐Layer Grown Zn1−xCdxSe/ZnSe Quantum Well

High Resolution Investigation on the Structure of Quantum Wells in the System CdSe-ZnSe

Epitaxial growth of thin films and quantum structures of II–VI visible-bandgap semiconductors

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Product

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Room‐Temperature Yellow Emission of a High Cd Content (x = 0.70), Highly Strained, Layer‐by‐Layer Grown Zn_1−xCd_xSe/ZnSe Quantum Well

Room‐Temperature Yellow Emission of a High Cd Content (x = 0.70), Highly Strained, Layer‐by‐Layer Grown Zn_1−xCd_xSe/ZnSe Quantum Well