Quaternary BeMgZnO by plasma-enhanced molecular beam epitaxy for BeMgZnO/ZnO heterostructure devices

Ullah, Md. Barkat; Toporkov, Mykyta; Avrutin, V.; Özgür, Ü.; Smith, David J.; Morkoç̌, H.

doi:10.1117/12.2260814

Cited by 4 publications

(3 citation statements)

References 30 publications

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“…Generally, the high angle grain boundaries which are the main structural defects that occur in the BeZnO solid solution were eliminated by the incorporation of Mg atoms with a small amount [52]. Moreover, x-ray study shows that the lattice strain which is present in the BeZnO due to the large different of covalent radii between Be (0.96 Å) and Zn (1.12 Å) atoms was reduced by the incorporation of Mg atoms which has a larger covalent radius of 1.41 Å, thus reduce the strain in BeMgZnO quaternary alloy [52,53]. The major advantage in this quaternary alloy is that Mg has a much larger covalent radius than Be atom which can composite the large lattice mismatch between ZnO and Be compounds [53].…”

Section: Alloys and Compundsmentioning

confidence: 99%

“…The case of Be 0.25 Mg 0.25 Zn 0.5 O and Be 0.25 Mg 0.5 Zn 0.25 O quaternary alloys and when introducing Be atoms by 25% the lattice constants remains nearly unchanged, but if the composition x on Be atom was moved to 50% the lattice constants decrease approximately by 3%. The lattice parameters of quaternary alloys deduced from deduced from XRD analysis [52]. Furthermore, the formation energy of the Be x Mg y Zn 1-x-y O quaternary alloys is calculated by the following mathematical representation:…”

Section: Alloys and Compundsmentioning

confidence: 99%

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An in-depth look at the structural, electronic, optical, and thermal properties of the cubic Be_xMg_yZn_1−x−yO quaternary alloys

Seksak,

Moussa,

Boudjelal

et al. 2024

Phys. Scr.

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In the present research work, the structural, electrical, optical, and thermodynamic properties of the BexMgyZn1−x-yO quaternary alloy were investigated. Its conventional structure, which is composed of the binary compounds ZnO, BeO, and MgO, and their ordered ternary alloys BexZn1−xO, BexMg1−xO, and MgxZn1−xO. A non-linear variation of lattice constants (a) and bulk modulus (B) as a function of the compositions (x, y) in BexMgyZn1−x-yO alloys is observed due to varying atomic radii of the constituent elements leading to the structural distortion against compositional changes. Both the ternary and quaternary alloys exhibit semiconducting properties, characterized by a direct bandgap ranging from 2-4 eV. This indicates their absorption and emission of light in the visible region of the spectrum, making them promising candidates for optoelectronic applications. The results of optical characteristics display the variation of refractive index and absorption coefficient of these alloys with respect to composition and wavelength. Present results will forecast the possible applications and guidelines for synthesizing such alloys under extreme conditions.

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Section: Alloys and Compundsmentioning

confidence: 99%

Section: Alloys and Compundsmentioning

confidence: 99%

An in-depth look at the structural, electronic, optical, and thermal properties of the cubic Be_xMg_yZn_1−x−yO quaternary alloys

Seksak,

Moussa,

Boudjelal

et al. 2024

Phys. Scr.

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“…Very high Mg content in the MgZnO barrier is required for achieving high 2DEG densities because of the partial cancellation of piezoelectric and spontaneous polarization charges at the heterointerface caused by compressive strain in MgZnO on ZnO. Alternatively, alloying ZnO concurrently with BeO and MgO, provides quaternary BeMgZnO barriers with tensile strain on ZnO, as BeO has lower (2.698 Å) and MgO has higher (theoretical 3.32 Å) in‐plane lattice parameter compared to ZnO (3.25 Å) . As a result, with the two aforementioned types of polarization charges operating in unison, sheet carrier concentrations as high as 1.2 × 10 13 cm −2 have been demonstrated for BeMgZnO/ZnO heterostructures …”

Section: Electron Mobilities Sheet Carrier Concentrations Schottky mentioning

confidence: 99%

Characterization of Ag Schottky Barriers on Be_0.02Mg_0.26ZnO/ZnO Heterostructures

Ullah

Ding

Nakagawara

et al. 2017

Physica Rapid Research Ltrs

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The BeMgZnO/ZnO heterostructures are capable of producing sufficiently high sheet electron densities to allow field effect transistor operation near or at the LO phonon plasmon resonance frequency for minimal LO phonon lifetimes and high electron velocity. Schottky barriers are imperative for the implementation of the aforementioned devices. Therefore, we have undertaken fabrication and characterization of Ag Schottky barriers on Zn-polar Be 0.02 Mg 0.26 ZnO/ZnO heterostructures, exhibiting the said two-dimensional electron gas (2DEG), grown by molecular beam epitaxy. Ag Schottky barriers are characterized by current-voltage (I-V) measurements in the temperature range from 80 to 400 K. At room temperature, the highest barrier height of 1.07 eV and an ideality factor of 1.22 are achieved with a rectification ratio of about eight orders of magnitude. Richardson constants of 38 AE 22 and 29 AE 20 A cm À2 K À2 are found using modified Richardson plots from Schottky diodes fabricated on two different structures. These values are consistent with the theoretical estimate of 36 A cm À2 K À2 for Be 0.02 Mg 0.26 ZnO. The temperature variation of barrier heights and ideality factors, an aberration from pure thermionic behavior, has been explained with plausible spatial inhomogeneity of barrier height with three Gaussian distributions in the temperature ranges of 80-200, 220-280, and 300-400 K.ZnO as a wide bandgap semiconductor [1] (%3.3 eV at room temperature) with high electron saturation velocity [2] (theoretical 3.5 Â 10 7 cm s À1 ), has garnered popularity owing to its potential for applications in thin film transparent transistors, transparent electrodes for solar cells, light emitters, chemical and biological sensors etc. [1,[3][4][5] Alloying with other II-VI oxides with higher bandgap (MgO and BeO) paves the way for heterojunction field effect transistors with polarization induced two-dimensional electron gas (2DEG). [6,7] Performance of such devices at high electric field, where electron transport is highly controlled by longitudinal optical (LO) phonons, [8] suffers due to accumulation of non-equilibrium hot LO phonons owing to strong electron-LO phonon coupling. Devices operating at or near plasmon-LO phonon resonance exhibit high electron drift velocity [9][10][11] allowed by ensuing ultrafast decay of hot LO phonons, [12,13] which leads to faster electron energy relaxation [14] and optimum device operation conditions (higher frequencies, lower degradation). [8] Plasmon-LO phonon resonance occurs when the energy of the LO phonon becomes similar to the plasmon energy, which occurs in ZnO at a bulk carrier concentration of %7 Â 10 18 cm À3 (ZnO LO phonon energy 72 meV). [14] Clearly, this is far beyond the MESFET operating window (typically 1 Â 10 17 À5 Â 10 17 cm À3 ). The necessity of high electron density makes the use of ZnO heterostructures with 2DEG imperative.Sheet carrier densities up to 8 Â 10 12 cm À2 (corresponding bulk concentration of 2 Â 10 19 cm À3 ) have been reported with MgZnO/ZnO heterostructu...

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Comparative study of BeMgZnO/ZnO heterostructures on c-sapphire and GaN by molecular beam epitaxy

Ding

Avrutin

Izyumskaya

et al. 2020

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Growth of ZnO directly on c-plane sapphire, with a large in-plane lattice mismatch of 18%, is relatively well understood for O-polar variety. However, the two-dimensional (2D) growth of Zn-polar ZnO on c-sapphire, needed for 2D electron gas formation, with low background electron density is in its infancy. While Zn-polar ZnO can be grown on GaN with the resulting small lattice mismatch (1.8%), the parallel conduction through GaN (bulk and/or surface) in fabricated BeMgZnO/ZnO heterostructure field effect transistors (HFETs) limits its utility for the time being. In this contribution, the authors report on the growth of high-quality Zn-polar BeMgZnO/ZnO HFET structures directly on sapphire substrates, in an effort to avoid the aforementioned parallel conduction, by employing an MgO and low-temperature ZnO buffer stack. The residual 2D equivalent concentration in the HFET structure on GaN is ∼2 × 1012 cm−2, which is detrimental, while highly resistive (>100 Ω.cm) Zn-polar ZnO layers with smooth surfaces on c-sapphire have been obtained via controlling the buffer stack growth conditions, which is vital to the realization of HFET device structures. Compared with the highest room temperature electron mobility of ∼250 cm2/V s in BeMgZnO/ZnO HFETs on GaN templates, a slightly lower electron mobility of ∼220 cm2/V s was achieved on c-sapphire due to a somewhat lower overall crystalline quality.

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Quaternary BeMgZnO by plasma-enhanced molecular beam epitaxy for BeMgZnO/ZnO heterostructure devices

Cited by 4 publications

References 30 publications

An in-depth look at the structural, electronic, optical, and thermal properties of the cubic Be_xMg_yZn_1−x−yO quaternary alloys

An in-depth look at the structural, electronic, optical, and thermal properties of the cubic Be_xMg_yZn_1−x−yO quaternary alloys

Characterization of Ag Schottky Barriers on Be_0.02Mg_0.26ZnO/ZnO Heterostructures

Comparative study of BeMgZnO/ZnO heterostructures on c-sapphire and GaN by molecular beam epitaxy

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Quaternary BeMgZnO by plasma-enhanced molecular beam epitaxy for BeMgZnO/ZnO heterostructure devices

Cited by 4 publications

References 30 publications

An in-depth look at the structural, electronic, optical, and thermal properties of the cubic Be x Mg y Zn1−x−y O quaternary alloys

An in-depth look at the structural, electronic, optical, and thermal properties of the cubic Be x Mg y Zn1−x−y O quaternary alloys

Characterization of Ag Schottky Barriers on Be0.02Mg0.26ZnO/ZnO Heterostructures

Comparative study of BeMgZnO/ZnO heterostructures on c-sapphire and GaN by molecular beam epitaxy

Contact Info

Product

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About

An in-depth look at the structural, electronic, optical, and thermal properties of the cubic Be_xMg_yZn_1−x−yO quaternary alloys

An in-depth look at the structural, electronic, optical, and thermal properties of the cubic Be_xMg_yZn_1−x−yO quaternary alloys

Characterization of Ag Schottky Barriers on Be_0.02Mg_0.26ZnO/ZnO Heterostructures