Alloying effects in organometallic vapor phase epitaxial grown ZnxCd1−xSe epilayers on (001) InP

Zhang, X.B.; Hark, S. K.

doi:10.1016/s0022-0248(01)00685-6

Cited by 4 publications

(6 citation statements)

References 8 publications

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“…We finally note that a peak of the rather similar energy of 2.04 eV has been obtained by cathodoluminescence from atomically ordered (Cd,Zn)Se alloy layers and has been attributed to agglomerates of the CdZnSe 2 compound as identified from X-ray diffraction superlattice reflections [2]. PL peaks around 2.05 eV were also observed in Zn(S,Se)/CdSe/Zn(S,Se) quantum well structures (with either 0 or 6 % S) and assigned to some structurally unidentified defects in the ZnSe and Zn(S,Se) layers [26].…”

Section: A Ii-vi Quantum Dotssupporting

confidence: 54%

“…Atomic ordering (and possibly phase separation) in W13. 5.4 epitaxial (Cd,Mn,Zn)(S,Se) with small or zero Mn content that manifests itself by luminescence peaks between 2 and 2.1 eV [2,[23][24][25][26], may, after all, not be a rarely occurring phenomenon. Fig.…”

Section: A Ii-vi Quantum Dotsmentioning

confidence: 99%

“…In recent years, atomic ordering and phase separation has also been observed in several heteroepitaxial II-VI systems, e.g. (Cd,Zn)Se [2][3][4], (Cd,Mn,Zn)Se [3,[5][6][7], (Fe,Zn)Se [8], (Cd,Zn)Te [9][10][11], and Cd(Se,Te) [12]. Atomic ordering and phase separation in IV-VI systems has, to the best of our knowledge, only been reported once in epitaxial (Pb,Eu)Te [13].…”

Section: Introductionmentioning

confidence: 98%

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Atomic Ordering in Self-assembled Epitaxial II-VI and IV-VI Compound Semiconductor Quantum Dot Systems

et al. 2002

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Transmission electron microcopy (TEM) in both the parallel illumination and scanning probe mode revealed atomically ordered entities within a 5 to 250 nm range in a IV-VI and a II-VI compound semiconductor quantum dot (QD) system. While the II-VI system was a nominal [001] CdSe/(Mn 0.1 Zn 0.9 )Se multilayer structure with the QDs embedded, the IV-VI system nominally consisted of [111] PbSe islands. The comparison of photoluminescence (PL) spectra from the CdSe/(Mn 0.1 Zn 0.9 )Se structure with those of a reference structure, that was grown to the same nominal specification under otherwise identical conditions except that no Mn was incorporated into the cladding layers, revealed for the former sample two peaks at approximately 2 and 2.1 eV. We tentatively attribute these two PL peaks to two groups of atomically ordered entities.

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Section: A Ii-vi Quantum Dotssupporting

confidence: 54%

Section: A Ii-vi Quantum Dotsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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Atomic Ordering in Self-assembled Epitaxial II-VI and IV-VI Compound Semiconductor Quantum Dot Systems

et al. 2002

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“…11 Of particular relevance is a study of phase separation for Zn x Cd 1-x Se epilayers grown on InP using organometallic vapor phase epitaxy which exhibited various mixed chemical phases having compositions, x, ranging from 0 to 1, as studied by cathodoluminescence (CL) and x-ray diffraction (XRD). 12 In our recent study of Zn x Cd 1-x Se/C core-shell nanocrystals, TEM showed twodimensional (2D) striations in the nanocrystals that are indicative of a composition modulation along a preferred crystallographic direction and reveal a chemical phase separation. 13 CL of these nanocrystals further showed that a composition modulation, x, of ~0.11 is consistent with a broadened emission and set of decomposed peaks in spatially integrated CL spectra.…”

Section: Introductionmentioning

confidence: 95%

Phase-separation in Zn_xCd_1-xSe/C Core/shell nanocrystals studied with cathodoluminescence spectroscopy

et al. 2010

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ZnxCd1-xSe/C core/shellnanocrystals with 31-39 nm diameter semiconductor cores and 11-25 nm-thick carbon shells were synthesized from solid state precursors. Transmission electron microscopy showed striations on a scale of ˜1 – 5 nm in the nanocrystals that are indicative of a composition modulation, and reveal a chemical phase separation and possible spinodal decomposition within the nanocrystals. Such a composition modulation within the ternary nanocrystals represents a rarely reported phenomenon that could lead to additional applications. The optical properties and carrier relaxation kinetics of the nanocrystals were examined with variable excitation cathodoluminescence (CL). As the excitation level is increased, carrier filling in two-dimensional (2D) phase-separated Cd-rich regions leads to a partial saturation of states before the onset of carrier filling in the higher bandgap homogenous Zn0.47Cd0.53Se regions. In order to model the state filling using Fermi-Dirac statistics for non-interacting carriers, a random quantum well model was used to determine the electron and hole eigensates in the Cd-rich regions of the nanocrystals.

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“…2 The growth of Zn x Cd 1Ϫx Se epilayers on a GaAs substrate showed that the alloy concentration in the epilayers is difficult to control when the growth method is organometallic vapor-phase epitaxy (OMVPE) 3,4 but not difficult to control when the method is molecular beam epitaxy. 6 Transmission electron microscopy (TEM) measurements showed that compositionally modulated (CM) superlattices have been formed at some places in these epilayers. 6 Transmission electron microscopy (TEM) measurements showed that compositionally modulated (CM) superlattices have been formed at some places in these epilayers.…”

Section: Introductionmentioning

confidence: 99%

Localization of excited carriers in organometallic vapor-phase epitaxial grown ZnxCd1−xSe epilayers with partial existence of lateral compositionally modulated superlattice

Zhang

Wong

Hark

2002

Journal of Elec Materi

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INTRODUCTIONThe Zn x Cd 1Ϫx Se alloy has been of great interest due to its potential applications in blue-green lasers and light emitting diodes. In the past years, attention in this regard was mainly paid to the growth and the study of Zn x Cd 1Ϫx Se low-dimensional structures, 1 while little attention was paid to Zn x Cd 1Ϫx Se epilayers. 2 The growth of Zn x Cd 1Ϫx Se epilayers on a GaAs substrate showed that the alloy concentration in the epilayers is difficult to control when the growth method is organometallic vapor-phase epitaxy (OMVPE) 3,4 but not difficult to control when the method is molecular beam epitaxy. 5 Recently, our growth of Zn x Cd 1Ϫx Se alloys on an InP substrate at 360°C by OMVPE showed that, despite a variation of growth parameters in a wide range, the alloy concentration does not change as we expected and is more likely to be found at x ϳ 0, 0.25, 0.5, 0.75, or 1. 6 Transmission electron microscopy (TEM) measurements showed that compositionally modulated (CM) superlattices have been formed at some places in these epilayers. 7 The TEM results suggest that the unusual alloy compositions at certain x values might be related to the spontaneous formation of a CM superlattice during the OMVPE growth. In fact, spontaneous formation of a CM superlattice has been observed in many III-V alloys and is being actively investigated due to the interests in their selforganized nature and their novel optical properties. 8,9 In this article, the photoluminescence (PL) properties of these alloys were studied. We found that, due to the partial existence of a CM superlattice in the epilayer and the smaller bandgap of the CM superlattice (relative to the normal random alloy), 8,9 the PL of the epilayer shows an anomalous red shift with a decrease in temperature and a large blue shift with an increase in excitation power. We propose a simple two-level model to quantitatively interpret the experimental observations. The structural and optical properties of organometallic vapor-phase epitaxial (OMVPE) grown Zn x Cd 1Ϫx Se epilayers on the (001) InP substrate were studied by transmission electron microscopy (TEM) and photoluminescence (PL). The TEM results showed the spontaneous formation of compositionally modulated (CM) superlattices along the [110] direction with a period of ϳ 10-20 nm at some places in the epilayer. In the PL measurements, we found an anomalous red shift of PL with a decrease in temperature (from 170 K to 100 K) and a large blue shift up to 40 meV with an increase in excitation power. We suggested that the anomalous red shift of PL is caused by a localization of photoexcited carriers from places containing a normal random alloy to places containing a CM superlattice, which has a narrower bandgap, and the large blue shift is caused by a saturation of energy states in the CM superlattice under high excitation. The narrower bandgap of the CM superlattice is supported by a polarized PL study, where the low energy part of PL is strongly polarized along the [110] direction, is consistent with the re...

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Alloying effects in organometallic vapor phase epitaxial grown ZnxCd1−xSe epilayers on (001) InP

Cited by 4 publications

References 8 publications

Atomic Ordering in Self-assembled Epitaxial II-VI and IV-VI Compound Semiconductor Quantum Dot Systems

Atomic Ordering in Self-assembled Epitaxial II-VI and IV-VI Compound Semiconductor Quantum Dot Systems

Phase-separation in Zn_xCd_1-xSe/C Core/shell nanocrystals studied with cathodoluminescence spectroscopy

Localization of excited carriers in organometallic vapor-phase epitaxial grown ZnxCd1−xSe epilayers with partial existence of lateral compositionally modulated superlattice

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Alloying effects in organometallic vapor phase epitaxial grown ZnxCd1−xSe epilayers on (001) InP

Cited by 4 publications

References 8 publications

Atomic Ordering in Self-assembled Epitaxial II-VI and IV-VI Compound Semiconductor Quantum Dot Systems

Atomic Ordering in Self-assembled Epitaxial II-VI and IV-VI Compound Semiconductor Quantum Dot Systems

Phase-separation in ZnxCd1-xSe/C Core/shell nanocrystals studied with cathodoluminescence spectroscopy

Localization of excited carriers in organometallic vapor-phase epitaxial grown ZnxCd1−xSe epilayers with partial existence of lateral compositionally modulated superlattice

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Product

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Phase-separation in Zn_xCd_1-xSe/C Core/shell nanocrystals studied with cathodoluminescence spectroscopy