Direct-to-indirect band gap crossover for the BexZn1−xTe alloy

Maksimov, O.; Tamargo, M. C.

doi:10.1063/1.1390327

Cited by 49 publications

(33 citation statements)

References 12 publications

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“…The DOS are plotted on the right panel of the figure. It is visually obvious that the observed bandgap is 2·61 eV which is well in accordance with the experimental observations reported by Maksimov and Tamargo (2001) who observed a crossover at x = 0·28 with a 2·77 eV bandgap. In figure 2, we give the electronic band structure and DOS for the Be 0·48 Zn 0·52 Te alloy having lattice match with the InP.…”

Section: Electronic Band Structure and Density Of Statessupporting

confidence: 92%

“…The MVCA shows -X crossover at x = 0·27. This is well in accordance with the experimentally reported composition x =0·28 (Maksimov and Tamargo 2001). The first-principles calculations have shown it to occur at x = 0·20 on the basis of five compositions including end compounds against fourteen compositions studied by us (de Almeida and Ahuja 2006).…”

Section: Figuresupporting

confidence: 84%

“…The results are in reasonable agreement with the measurements. Knowing that Maksimov and Tamargo (2001) performed measurements on the epilayers at room temperature and subtle stoichiometric uncertainties remaining in the samples, our results may be taken to be in very good agreement. It is well known for zinc chalcogenides that in the X c 1,3 states charge is between the constituents.…”

Section: Figuresupporting

confidence: 54%

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Electronic properties and charge density of Be x Zn1 − x Te alloys

Swarnkar¹,

Paliwal

Patel

et al. 2011

Bull Mater Sci

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Electronic band structure calculations are performed for the Be x Zn 1−x Te (0≤x≤1 in steps of 0·2) alloys following the empirical pseudopotential method. The alloying effects are modelled through the modified virtual crystal approximation. Throughout the composition, valence band maximum resides at the point. The conduction band minimum, however, shifts from to X point of symmetry when x = 0·27. The observed crossover from direct to indirect bandgap is well in accordance with the experimental observations. Effect of alloying on the density of states is also discussed. The charge density distribution along a few major planes is computed and discussed. The electronic band structure related parameters like bandwidths, bandgaps and ionicity are reported and compared with experimental data wherever available. We also give estimates of cohesive energy and bulk modulus for the alloys.

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Section: Electronic Band Structure and Density Of Statessupporting

confidence: 92%

Section: Figuresupporting

confidence: 84%

Section: Figuresupporting

confidence: 54%

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Electronic properties and charge density of Be x Zn1 − x Te alloys

Swarnkar¹,

Paliwal

Patel

et al. 2011

Bull Mater Sci

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“…Thus the PL peak was ascribed not to the direct gap emission but to another origin. Figure 2 shows the PL peak and the direct gap energies as a function of Be composition (x), where the Γ-X indirect gap energy of Be 0.48 Zn 0.52 Te (i.e., x = 0.48) [3] is given with the symbol ( * ). The PL peak energy agrees well with the direct gap energy when x is from 0 to 0.3.…”

Section: Characterization Of Beznsete Quaternariesmentioning

confidence: 99%

Proposal of a novel BeZnSeTe quaternary for II‐VI middle range visible light emitting devices on InP substrates

Takashima

Nomura

Nakai

et al. 2004

Physica Status Solidi (b)

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A novel BeZnSeTe quaternary has been proposed for active layers of II-VI visible light emitting devices on InP substrates. BeZnSeTe, which lattice parameters were matched to InP, were grown on InP substrates by molecular beam epitaxy (MBE). The Be composition was changed from 0.11 to 0.35. The photoluminescence (PL) spectra of these samples at 15 K showed single peak emissions with wavelengths from 487 to 506 nm without any deep level emission. From the reflectivity and PL spectra at 15 K, the Γ-Γ direct and Γ-X indirect bandgaps of BeZnSeTe were evaluated, and it is shown that the crossover point from direct to indirect is around Be composition of 0.3. Applying the BeZnSeTe for the active layer, visible light emitting diodes (LEDs) were fabricated on InP substrates by MBE, resulting in yellow light single peak emissions around 575 nm at room temperature. [1,2]. In this structure, however, hole injection into the active layer was obstructed by the valence-band discontinuity between the active and p-cladding layers because of their type-II band lineup, which deteriorates the device characteristics.In this paper, novel BeZnSeTe quaternaries are proposed to solve this problem. By applying BeZnSeTe for active layers instead of ZnCdSe, the valence band top shifts toward the higher electron energy, by which the valence band discontinuity of concern can be decreased or disappeared. As the bandgap energy of BeZnSeTe can be controlled in the range from 2.1 to 2.7 eV keeping lattice-matching to InP, so yellow-to-blue color light emissions are expected. Meanwhile the incorpolation of BeSe and BeTe into the crystal contributes to enhancing the lattice-hardness, which may be effective to lengthening the device lifetime. In the experiment, BeZnSeTe quaternaries were grown on InP substrates by molecular beam epitaxy (MBE). The photoluminescence (PL) and light reflectivity spectra of BeZnSeTe were measured at 15 K to evaluate the Γ-Γ direct and Γ-X indirect bandgaps. By that, the direct-to-indirect crossover is discussed. Visible light emitting diodes (LEDs) with BeZnSeTe active layers were fabricated, observing the yellow light single-peak emission around 575 nm at room temperature.

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“…In this study, however, the indirect energy gap such as the X-band energy has not been investigated for this alloy. Recently the direct-to-indirect crossover of BeZnTe was discussed showing that BeZnTe has an indirect bandgap of 2.77 eV at the lattice matching point [42]. The p-type BeZnTe was grown with RF radical nitrogen doping, to evaluate the hole concentration at room temperature by the van der Pauw method.…”

Section: Characteristics Of Bezntementioning

confidence: 99%

Yellow‐green emitters based on beryllium‐chalcogenides on InP substrates

Kishino

Nomura

2004

phys. stat. sol. (c)

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PACS 78.20.Ci, 78.55.Et, 78.66.Hf, 81.05.Dz, 81.15.Hi, 85.60.Jb II-VI compound materials containing beryllium-chalcogenides such as BeZnTe, ZnCdSe/BeZnTe, and MgSe/BeZnTe superlattices grown on InP substrates have been investigated for yellow-green emitters employing molecular beam epitaxy. Photoluminescence peaks of ZnCdSe/BeZnTe superlattices were widely controlled from 740 to 507 nm by changing the layer thickness combination. Applying ZnCdSe/BeZnTe and MgSe/BeZnTe superlattices, visible light emitting diodes (LEDs) were fabricated emitting at the wavelengths from 554 (yellow-green) to 644 nm (red) at room temperature. For yellow (575nm) LEDs, a long lifetime more than 3500 hours was demonstrated. Laser diodes consisting of a ZnCdSe active, a MgSe/ZnCdSe superlattice n-cladding, and a MgSe/BeZnTe superlattice p-cladding layers successfully operated with yellow-green lasing emissions around 560 nm at 77 K.

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Direct-to-indirect band gap crossover for the BexZn1−xTe alloy

Cited by 49 publications

References 12 publications

Electronic properties and charge density of Be x Zn1 − x Te alloys

Electronic properties and charge density of Be x Zn1 − x Te alloys

Proposal of a novel BeZnSeTe quaternary for II‐VI middle range visible light emitting devices on InP substrates

Yellow‐green emitters based on beryllium‐chalcogenides on InP substrates

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