ZnO based oxide system with continuous bandgap modulation from 3.7 to 4.9 eV

Yang, Chan; Li, X. M.; Gu, Yongqiang; Wang, Yu; Gao, Xiangdong; Zhang, Y. W.

doi:10.1063/1.2987420

Cited by 68 publications

(36 citation statements)

References 14 publications

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“…In order to realize such optoelectronic devices with high efficiency, a crucial step is the realization of band gap engineering by alloying to create barrier layers and quantum wells (QWs) in device heterostructures [3]. Many works have been reported on ZnMgO [4], ZnCaO [5,6], and ZnBeO [7,8], which are wide band gap semiconductors, for application in quantum well-related devices and other fields from the viewpoint of band gap engineering as well as p-n junctions [9].…”

Section: Introductionmentioning

confidence: 99%

Fabrication of high-quality ZnCdO epilayers and ZnO/ZnCdO heterojunction on sapphire substrates by pulsed laser deposition

Yao

Tang

et al. 2015

Applied Surface Science

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Section: Introductionmentioning

confidence: 99%

Fabrication of high-quality ZnCdO epilayers and ZnO/ZnCdO heterojunction on sapphire substrates by pulsed laser deposition

Yao

Tang

et al. 2015

Applied Surface Science

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“…7,[10][11][12][13] The advantage of this quaternary system is that Mg has a much larger covalent radius (1.41 Å ) 6 than Be and can compensate for the large lattice mismatch between ZnO and BeO. Therefore, it is expected that by tuning the compositions of both BeO and MgO in ZnO (i.e., Be/Mg ratio), one can achieve lattice matching to ZnO, prevent phase separation, and achieve wider bandgaps.…”

Section: Introductionmentioning

confidence: 99%

Lattice parameters and electronic structure of BeMgZnO quaternary solid solutions: Experiment and theory

Toporkov

Demchenko

Zolnai

et al. 2016

Journal of Applied Physics

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BexMgyZn1−x−yO semiconductor solid solutions are attractive for UV optoelectronics and electronic devices owing to their wide bandgap and capability of lattice-matching to ZnO. In this work, a combined experimental and theoretical study of lattice parameters, bandgaps, and underlying electronic properties, such as changes in band edge wavefunctions in BexMgyZn1−x−yO thin films, is carried out. Theoretical ab initio calculations predicting structural and electronic properties for the whole compositional range of materials are compared with experimental measurements from samples grown by plasma assisted molecular beam epitaxy on (0001) sapphire substrates. The measured a and c lattice parameters for the quaternary alloys BexMgyZn1−x with x = 0−0.19 and y = 0–0.52 are within 1%–2% of those calculated using generalized gradient approximation to the density functional theory. Additionally, composition independent ternary BeZnO and MgZnO bowing parameters were determined for a and c lattice parameters and the bandgap. The electronic properties were calculated using exchange tuned Heyd-Scuseria-Ernzerhof hybrid functional. The measured optical bandgaps of the quaternary alloys are in good agreement with those predicted by the theory. Strong localization of band edge wavefunctions near oxygen atoms for BeMgZnO alloy in comparison to the bulk ZnO is consistent with large Be-related bandgap bowing of BeZnO and BeMgZnO (6.94 eV). The results in aggregate show that precise control over lattice parameters by tuning the quaternary composition would allow strain control in BexMgyZn1−x−yO/ZnO heterostructures with possibility to achieve both compressive and tensile strain, where the latter supports formation of two-dimensional electron gas at the interface.

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“…void of phase separation, as compared to ternary MgZnO or BeZnO alloys. For certain growth conditions quaternary layers with sufficiently large bandgaps up to 4.9 eV [8] have been achieved. Theoretical studies of bandgap variation and equilibrium lattice parameters for the quaternary BeMgZnO system have been performed mainly using density functional theory (DFT), known to significantly underestimate the bandgap [10,11].…”

Section: Introductionmentioning

confidence: 99%

“…Unfortunately, use of nominal high temperatures for attaining quality material, the bandgap tuning is limited because of phase segregation for Mg contents above 33% induced by structural mismatch between the wurtzite ZnO and rock salt MgO [7]. To overcome this limitation, quaternary BeMgZnO has been proposed [1,8,9]. As initial experiments and theoretical studies revealed, co-alloying of ZnO together with BeO and MgO results in more stable wurtzite structure, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Due to such limitations, the Be content after sample preparation is sometimes given by an effective parameter, e.g. the number of laser pulses ablated on BeO target during the pulsed laser deposition (PLD) of BeMgZnO layers [8] or cell temperature during molecular beam epitaxy (MBE) growth [14]. Such descriptions lack the specificity needed for direct quantitative comparison of theory and experiment in engineering and understanding the structural and optical properties of BeZnO and BeMgZnO alloys.…”

Section: Introductionmentioning

confidence: 99%

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Nondestructive atomic compositional analysis of BeMgZnO quaternary alloys using ion beam analytical techniques

Zolnai

Toporkov

Volk

et al. 2015

Applied Surface Science

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HighlightsBeMgZnO thin layers were grown with plasma assisted molecular beam epitaxy (MBE)The Be contents were accurately measured with RBS and proton elastic backscattering The Tauc bandgap was measured from optical transmittance experiments The bandgap has been varied between 3.26 eV and 4.62 eV via the Be and Mg content Experimental and density functional theory calculated bandgaps were in good agreement AbstractThe atomic composition with less than 1-2 atom % uncertainty was measured in ternary BeZnO and quaternary BeMgZnO alloys using a combination of nondestructive Rutherford backscattering spectrometry with 1 MeV He + analyzing ion beam and nonRutherford elastic backscattering experiments with 2.53 MeV energy protons. An enhancement factor of 60 in the cross-section of Be for protons has been achieved to monitor Be atomic concentrations. Usually the quantitative analysis of BeZnO and BeMgZnO systems is challenging due to difficulties with appropriate experimental tools for the detection of the light Be element with satisfactory accuracy. As it is shown, our applied ion beam technique, Page 2 of 22A c c e p t e d M a n u s c r i p t supported with the detailed simulation of ion stopping, backscattering, and detection processes allows of quantitative depth profiling and compositional analysis of wurtzite BeZnO/ZnO/sapphire and BeMgZnO/ZnO/sapphire layer structures with low uncertainty for both Be and Mg. In addition, the excitonic bandgaps of the layers were deduced from optical transmittance measurements. To augment the measured compositions and bandgaps of BeO and MgO co-alloyed ZnO layers, hybrid density functional bandgap calculations were performed with varying the Be and Mg contents. The theoretical vs. experimental bandgaps show linear correlation in the entire bandgap range studied from 3.26 eV to 4.62 eV. The analytical method employed should help facilitate bandgap engineering for potential applications, such as solar blind UV photodetectors and heterostructures for UV emitters and intersubband devices.

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ZnO based oxide system with continuous bandgap modulation from 3.7 to 4.9 eV

Cited by 68 publications

References 14 publications

Fabrication of high-quality ZnCdO epilayers and ZnO/ZnCdO heterojunction on sapphire substrates by pulsed laser deposition

Fabrication of high-quality ZnCdO epilayers and ZnO/ZnCdO heterojunction on sapphire substrates by pulsed laser deposition

Lattice parameters and electronic structure of BeMgZnO quaternary solid solutions: Experiment and theory

Nondestructive atomic compositional analysis of BeMgZnO quaternary alloys using ion beam analytical techniques

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