Temperature dependence of localization effects of excitons in ZnO∕CdxZn1−xO∕ZnO double heterostructures

Lange, M.; Zippel, Jan; Benndorf, G.; Czekalla, C.; Hochmuth, H.; Lorenz, Michael; Grundmann, Marius

doi:10.1116/1.3138002

Cited by 16 publications

(15 citation statements)

References 29 publications

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“…In the case of strongly localized excitons, the opposite effect may occur as not all excitons contribute to phonon replicas. 20,72 This effect can result in the determination of too small values of S, particularly in confined structures such as quantum dots and quantum wells. Consequently, only the intensities of the phonon replicas without the ZPL should be analyzed.…”

Section: Phonon Replica and Two Electron Satellitesmentioning

confidence: 99%

“…Following these reports, several authors adopted this interpretation for different ZnO samples. 15,20,[34][35][36][37] However, a convergent picture concerning the defect identification and the electronic properties of the 3.333 eV line has not yet emerged as evidenced by the large variety of contradicting explanations for this emission in recent years. Even less is known about the often weaker lines between 3.33 and 3.35 eV which sporadically appear in combination with the Y 0 transition.…”

Section: Introductionmentioning

confidence: 96%

“…This line was reported in a multitude of different ZnO samples such as substrates, 3-6 homoepitaxial 7-9 and heteroepitaxial films, [10][11][12][13] microcrystals and nanocrystals, [14][15][16][17][18] nanowires, 19 and quantum wells. 20 In nanomaterials the Y 0 line is only observed in structures with sufficiently large dimensions. Stichtenoth et al 19 observed the Y 0 emission in ZnO nanowires with diameters greater than 100 nm, whereas it is not observed in nanowires with smaller diameters.…”

Section: Introductionmentioning

confidence: 99%

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Bound excitons in ZnO: Structural defect complexes versus shallow impurity centers

et al. 2011

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ZnO single crystals, epilayers, and nanostructures often exhibit a variety of narrow emission lines in the spectral range between 3.33 and 3.35 eV which are commonly attributed to deeply bound excitons (Y lines). In this work, we present a comprehensive study of the properties of the deeply bound excitons with particular focus on the Y 0 transition at 3.333 eV. The electronic and optical properties of these centers are compared to those of the shallow impurity related exciton binding centers (I lines). In contrast to the shallow donors in ZnO, the deeply bound exciton complexes exhibit a large discrepancy between the thermal activation energy and localization energy of the excitons and cannot be described by an effective mass approach. The different properties between the shallow and deeply bound excitons are also reflected by an exceptionally small coupling of the deep centers to the lattice phonons and a small splitting between their two electron satellite transitions. Based on a multitude of different experimental results including magnetophotoluminescence, magnetoabsorption, excitation spectroscopy (PLE), time resolved photoluminescence (TRPL), and uniaxial pressure measurements, a qualitative defect model is developed which explains all Y lines as radiative recombinations of excitons bound to extended structural defect complexes. These defect complexes introduce additional donor states in ZnO. Furthermore, the spatially localized character of the defect centers is visualized in contrast to the homogeneous distribution of shallow impurity centers by monochromatic cathodoluminescence imaging. A possible relation between the defect bound excitons and the green luminescence band in ZnO is discussed. The optical properties of the defect transitions are compared to similar luminescence lines related to defect and dislocation bound excitons in other II-VI and III-V semiconductors.

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Section: Phonon Replica and Two Electron Satellitesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Bound excitons in ZnO: Structural defect complexes versus shallow impurity centers

et al. 2011

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“…[9][10][11][12][13] However, fabrication of ZnCdO films and heterostrctures by pulsed laser deposition (PLD) is rarely reported. 5,[14][15][16][17] Recent works on the optical properties of GaN-based QWs have shown that localized exciton transitions always dominate in this system at low temperatures 18,19 and the degree of carrier localization is strongly correlated with the composition concentrations, well width, and interface roughness. 20,21 The understanding of carrier dynamics is essential for the lasing application.…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of weak localization effects of excitons in ZnCdO/ZnO single quantum well

Yang

Chen

Liu

et al. 2011

Journal of Applied Physics

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We report on the optical properties of high-quanlity ZnCdO/ZnO single quantum well (SQW) grown on c-sapphire substrates by pulsed laser deposition. The temperature dependent photoluminescence (PL) of ZnO/ZnCdO SQWs exhibits an inconspicuous S-shaped property due to the weak carrier localization effect, as a consequence of the slightly inhomogeneous Cd distribution in the well layer as well as the smooth interfaces. The integrated PL intensity of the higher Cd SQW decreases faster than that of the lower sample with increasing temperature, indicating the presence of interface barrier in high Cd content SQWs.

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“…Recently, some researchers have reported various findings concerning Cd x Zn 1−x O / ZnO QWs, [5][6][7] although its emission mechanisms remain poorly understood. Alloy disorder and phase separation in alloy semiconductors are derived from differences in the chemical nature of cations, which mainly influence the excitonic recombination processes of QWs.…”

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confidence: 99%

Band alignment and excitonic localization of ZnO/Cd0.08Zn0.92O quantum wells

Matsui

Osone

Tabata

2010

Journal of Applied Physics

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Study of the band alignment in (Zn,Cd)Se/ZnSe quantum wells by means of photoluminescence excitation spectroscopy Measurement of the critical thickness of ZnCdSe quantum wells in ZnSe barrier layers by the piezoelectric effect Appl.The band structure and excitonic recombination of a Cd 0.08 Zn 0.92 O / ZnO single quantum well ͑SQW͒ were shown to vary according to well width ͑L W ͒. The excitonic localization of a Cd 0.08 Zn 0.92 O single layer used as a well layer of the SQW was based on alloy disorder by spatial inhomogeneity of the Cd atoms. It was shown that photoexcited excitons localized into potential fluctuations of 18 meV from a measurement of temperature-dependent photoluminescence ͑PL͒, which became an important guide to estimate the degree of excitonic localization for the SQW. The L W of SQW remarkably influenced excitonic localization, which gradually increased with a narrowing of L W . When L W was less than the excitonic Bohr diameter ͑R ex : 3.6 nm͒ of ZnO, the excitonic localization was determined by both alloy disorder and interface fluctuations of the barrier/ well interfaces. On the other hand, the excitonic localization became remarkably weak for L W greater than R ex mainly because of the quantum-confined Stark effect ͑QCSE͒. The formation of the QCSE was clarified by an excitation-power-dependent PL of SQW and an identification of band alignment of a Cd 0.08 Zn 0.92 O / ZnO heterostructure. Finally, the excitonic localization of SQW for L W comparable to R ex was determined by the alloy disorder generated in the well.

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Temperature dependence of localization effects of excitons in ZnO∕CdxZn1−xO∕ZnO double heterostructures

Cited by 16 publications

References 29 publications

Bound excitons in ZnO: Structural defect complexes versus shallow impurity centers

Bound excitons in ZnO: Structural defect complexes versus shallow impurity centers

Temperature dependence of weak localization effects of excitons in ZnCdO/ZnO single quantum well

Band alignment and excitonic localization of ZnO/Cd0.08Zn0.92O quantum wells

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