Valence band offset of the ZnO/AlN heterojunction determined by x-ray photoemission spectroscopy

Veal, T. D.; King, P. D. C.; Hatfield, S. A.; Bailey, LR; McConville, Christopher F; Martel, Bernard; Moreno, J. C.; Frayssinet, Éric; Sèmond, F.; Zúñiga‐Pérez, Jesús

doi:10.1063/1.3032911

Cited by 84 publications

(50 citation statements)

References 34 publications

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“…As far as we are concerned here with rather low In-content, typically x<35%, our results show that In x Al 1-x N/ZnO and In x Ga 1-x N/ZnO are both type II heterostructures. Our results are consistent with ab-initio those reported by Van de Walle et al [4], and with recent photo-emission spectroscopy ones [10,11]. They also agree very well with those given by Yang et al [3] which have shown the strong anisotropy of the energy band lineup at the interface of an InN/ZnO heterostructure.…”

Section: Energy Band-offsetssupporting

confidence: 95%

Theoretical study of In_xAl_1‐xN/ZnO and In_xGa_1‐xN/ZnO strained quantum well lasers

Djellal

Kadri

Gil

et al. 2011

Phys. Status Solidi C

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We perform a theoretical study of InxAl1‐xN/ZnO and InxGa1‐xN/ZnO strained Quantum Well (QW) Lasers oriented along the non‐polar A‐plane axis. In order to determine the energy band‐offsets in both heterostructures as a function of alloy composition, we use the ab‐initio method to compute the total energies of these systems. Then, we use the k·P method within the envelop function formalism to study conduction and valence energy subband structures for various alloy compositions and well widths. Finally, we calculate the Laser gain for such strained QW heterostructures. Our results show that type I heterostructures can be made with two kind of systems: InxGa1‐xN/InxAl1‐xN/ZnO and InxGa1‐xN/InyGa1‐yN/ZnO where InxGa1‐xN is the QW in both cases. These heterostructures are lattice‐matched along A‐plane axis at x=32% in InxAl1‐xN/ZnO and x=17% in InxGa1‐xN/ZnO. However, because of the anisotropy of the built‐in strain at the interface, they are still slightly compressively strained along c‐axis. Pure tensile strain or pure compressive can be achieved only at In‐content values well below or well above these critical values, respectively. Our results are compared with various theoretical and experimental values, and quite good agreement is found. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Section: Energy Band-offsetssupporting

confidence: 95%

Theoretical study of In_xAl_1‐xN/ZnO and In_xGa_1‐xN/ZnO strained quantum well lasers

Djellal

Kadri

Gil

et al. 2011

Phys. Status Solidi C

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“…Indeed, from direct measurements, measurements of valence band offsets (allowing band alignment relative to the CNL), and theoretical calculations [63,135,[163][164][165][166][167], the CNL has been found to occur above the CBM across the TCOs, as summarized in Fig. 11.…”

Section: Overriding Explanation?mentioning

confidence: 99%

Conductivity in transparent oxide semiconductors

King

Veal

2011

J. Phys.: Condens. Matter

224

180

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Abstract. Despite an extensive research effort for over 60 years, an understanding of the origins of conductivity in wide band-gap transparent conducting oxide (TCO) semiconductors remains elusive. While TCOs have already found widespread use in device applications requiring a transparent contact, there are currently enormous efforts to (i) increase the conductivity of existing materials, (ii) identify suitable alternatives, and (iii) attempt to gain semiconductor-engineering levels of control over their carrier density, essential for the incorporation of TCOs into a new generation of multifunctional transparent electronic devices. These efforts, however, are dependent on a microscopic identification of the defects and impurities leading to the high unintentional carrier densities present in these materials. Here, we review recent developments towards such an understanding. While oxygen vacancies are commonly assumed to be the source of the conductivity, there is increasing evidence that this is not a sufficient mechanism to explain the total measured carrier concentrations. In fact, many studies suggest that oxygen vacancies are deep, rather than shallow, donors, and their abundance in as-grown material is also debated. We discuss other potential contributions to the conductivity in TCOs, including other native defects, their complexes, and in particular hydrogen impurities. Convincing theoretical and experimental evidence is presented for the donor nature of hydrogen across a range of TCO materials, and while its stability and the presence of interstitial and substitutional species are still somewhat open questions, it is one of the leading contenders for unintentional conductivity in TCOs. We also review recent work indicating that the surfaces of TCOs can support very high carrier densities, opposite to the case of conventional semiconductors. In thin-film materials/devices and, in particular, nanostructures, the surface can have a large impact on the total conductivity in TCOs. We discuss models that attempt to explain both the bulk and surface conductivity based on features of the bulk band structure common across the TCOs, and compare these materials to other semiconductors. Finally, we briefly consider transparency in these materials, and its interplay with conductivity. Understanding this interplay, as well as the microscopic contenders for the conductivity of these materials, will prove essential to the future design and control of TCO semiconductors, and their implementation into novel multifunctional devices.

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“…1(d) and (f). The VBM positions in the VB spectra were determined by linear extrapolation of the leading edges of VB spectra to the base lines in order to account for the finite www.pss-b.com instrument resolution [15,16]. The scatter of the data with respect to the fit are estimated as uncertainty in VBM positions of less than 0.04 eV, which are also estimated from fitting with different parameters.…”

mentioning

confidence: 99%

Determination of MBE grown wurtzite GaN/Ge₃N₄/Ge heterojunctions band offset by X‐ray photoelectron spectroscopy

Kumar

Rajpalke

Roul

et al. 2011

Physica Status Solidi (b)

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Hexagonal Ge3N4 layer was prepared on Ge surface by in situ direct atomic source nitridation and it is promising buffer layer to grow GaN on Ge (111). The valence band offset (VBO) of GaN/Ge3N4/Ge heterojunctions is determined by X‐ray photoemission spectroscopy. The valence band (VB) of Ge3N4 is found to be 0.38 ± 0.04 eV above the GaN valance band and 1.14 ± 0.04 eV below the Ge. The GaN/Ge3N4 and Ge3N4/Ge are found type‐II and type‐I heterojunctions, respectively. The exact measurements of the VBO and conduction band offset (CBO) are important for use of GaN/Ge3N4/Ge (111) heterosystems.

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Valence band offset of the ZnO/AlN heterojunction determined by x-ray photoemission spectroscopy

Cited by 84 publications

References 34 publications

Theoretical study of In_xAl_1‐xN/ZnO and In_xGa_1‐xN/ZnO strained quantum well lasers

Theoretical study of In_xAl_1‐xN/ZnO and In_xGa_1‐xN/ZnO strained quantum well lasers

Conductivity in transparent oxide semiconductors

Determination of MBE grown wurtzite GaN/Ge₃N₄/Ge heterojunctions band offset by X‐ray photoelectron spectroscopy

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Valence band offset of the ZnO/AlN heterojunction determined by x-ray photoemission spectroscopy

Cited by 84 publications

References 34 publications

Theoretical study of InxAl1‐xN/ZnO and InxGa1‐xN/ZnO strained quantum well lasers

Theoretical study of InxAl1‐xN/ZnO and InxGa1‐xN/ZnO strained quantum well lasers

Conductivity in transparent oxide semiconductors

Determination of MBE grown wurtzite GaN/Ge3N4/Ge heterojunctions band offset by X‐ray photoelectron spectroscopy

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Product

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Theoretical study of In_xAl_1‐xN/ZnO and In_xGa_1‐xN/ZnO strained quantum well lasers

Theoretical study of In_xAl_1‐xN/ZnO and In_xGa_1‐xN/ZnO strained quantum well lasers

Determination of MBE grown wurtzite GaN/Ge₃N₄/Ge heterojunctions band offset by X‐ray photoelectron spectroscopy