Electronic structure of ZnO:GaN compounds: Asymmetric bandgap engineering

Huda, M. N.; Yan, Yanfa; Wei, Su‐Huai; Al‐Jassim, Mowafak

doi:10.1103/physrevb.78.195204

Cited by 111 publications

(124 citation statements)

References 22 publications

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“…The design of novel functional semiconductors with given values of the energy band gap is an area of intense research 1,2,3,4,5 . In particular, much attention is focused on the band gap engineering of group-III nitride semiconductors, whose remarkable optical properties are important for optoelectronic device applications 6,7 .…”

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Hybrid density functional calculations of the band gap ofGaxIn1−xN

Walter

Rappe

et al. 2009

Phys. Rev. B

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Recent theoretical work has provided evidence that hybrid functionals, which include a fraction of exact (Hartree Fock) exchange in the density functional theory (DFT) exchange and correlation terms, significantly improve the description of band gaps of semiconductors compared with local and semilocal approximations. Based on a recently developed order-N method for calculating the exact exchange in extended insulating systems, we have implemented an efficient scheme to determine the hybrid functional band gap. We use this scheme to study the band gap and other electronic properties of the ternary compound In1−xGaxN using a 64-atom supercell model. The design of novel functional semiconductors with given values of the energy band gap is an area of intense research 1,2,3,4,5 . In particular, much attention is focused on the band gap engineering of group-III nitride semiconductors, whose remarkable optical properties are important for optoelectronic device applications 6,7 . To guide the search for compounds with tailored properties 1 , experimental studies are often accompanied by electronic structure calculations based on density functional theory (DFT)8 . For these calculations, the local-density(LDA) or generalized gradient approximations(GGA) are typically used. Due to the delocalization error of the LDA and GGA exchange and correlation functionals, however, these approaches severely underestimate the materials band gaps 9,10 .As shown by several recent studies 11 , a significant improvement in the description of semiconductor and insulator band gaps is generally obtained by using hybrid functionals 12 , in which some exact (Hartree-Fock) exchange is mixed into the exchange and correlation functional. This reduces the delocalization and derivative discontinuity errors of (semi)local functionals 2,9,10,11 . However, because of the considerable computational cost of evaluating the non-local exact exchange term, hybrid functionals have been mostly applied to systems with small unit cells 13 . For the modeling of systems where a large supercell is needed, an additional screened exchange approximation is usually made to relieve the computational burden 2,11 . Recently Wu et al. (WSC)14 introduced an order-N method to calculate the exact exchange in extended insulating systems. The WSC method is based on a localized Wannier function representation of the occupied (valence) space, so that the exchange interaction between two orbitals decays rapidly with the distance between their centers. A truncation can thus be introduced, which greatly reduces the computational cost. The effectiveness of the WSC method was demonstrated by ground state electronic minimizations for crystalline silicon in supercells with 64 and 216 atoms.In this paper, we extend the WSC scheme to compute hybrid functional band gaps. To this end, the system's first (few) empty conduction state(s) is(are) determined starting from the ground state calculated via the WSC method. With hybrid functionals, this requires the computation of the pair exchange ...

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confidence: 99%

Hybrid density functional calculations of the band gap ofGaxIn1−xN

Walter

Rappe

et al. 2009

Phys. Rev. B

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“…Although, this can be partially overcome by using LDA+U or GGA+U strategy, the calculated band gaps are still much lower than the experimental values. 9,15 Therefore, the ∆E VBO values given by using these functionals remain doubtful.…”

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confidence: 99%

“…Considerable efforts have been made to determine this parameter both experimentally [10][11][12] and theoretically. [13][14][15] However, these works gave quite different values. For example, Hong et al measured the valence band offset (∆E VBO ) at a ZnO/GaN (0001) heterointerface by means of ex situ ultraviolet and x-ray photoemission spectroscopy (UPS/XPS).…”

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Hybrid density functional study of band alignment in ZnO–GaN and ZnO–(Ga1−xZnx)(N1−xOx)–GaN heterostructures

Wang

Zhao

Wang

et al. 2012

Phys. Chem. Chem. Phys.

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“…17,18 Theoretical study of GaN/ZnO super-lattice and random-alloy has provided important insights and guidelines for designing band gap reduction. 19 However, the band offset and build-in electric filed at the interface of ZnO/GaN core/shell NWs have never been reported. Compared with other core/shell NWs, 8,9 ZnO/GaN has a very small lattice mismatch (~1.86%) and thus low interface strain.…”

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Natural charge spatial separation and quantum confinement of ZnO/GaN-core/shell nanowires

Wang

Fan

Zhao

2010

Journal of Applied Physics

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We performed density-functional calculations to investigate the electronic structure of ZnO/GaN core/shell heterostructured nanowires (NWs) orientating along <0001> direction. The build-in electric filed arising from the charge redistribution at the } 00 1 1 { interfaces and the band offsets were revealed. ZnO-core/GaN-shell NWs rather than GaN-core/ZnO-shell ones were predicted to exhibit natural charge spatial separation behaviors, which are understandable in terms of an effective mass model. The effects of quantum confinement on the band gaps and band offsets were also discussed.Quasi-one-dimensional semiconductor nanostructures are increasingly used in photonic and electronic devices, such as integrated nanodevices, 1 novel field effect transistors (FET) core/shell NWs have demonstrated the accumulation of ZnO-core, Ge-core hole gas and GaN-core electron gas, in agreement with experimental observations. Moreover, the band offset of core-shell NWs can be modulated by the quantum confinement effect and the strain induced by the lattice mismatch between the two components, yielding a board range of band gaps, which facilitates light adsorption of PV devices. The core-shell NWs with type-II band alignment are advantageous in promising solar energy applications such as water splitting, dye-sensitized and even regular solar cells. [13][14][15]

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Electronic structure of ZnO:GaN compounds: Asymmetric bandgap engineering

Cited by 111 publications

References 22 publications

Hybrid density functional calculations of the band gap ofGaxIn1−xN

Hybrid density functional calculations of the band gap ofGaxIn1−xN

Hybrid density functional study of band alignment in ZnO–GaN and ZnO–(Ga1−xZnx)(N1−xOx)–GaN heterostructures

Natural charge spatial separation and quantum confinement of ZnO/GaN-core/shell nanowires

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