Heterojunction band offset engineering

Franciosi, A.; Walle, Chris G. Van de

doi:10.1016/0167-5729(95)00008-9

Cited by 448 publications

(157 citation statements)

References 291 publications

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“…There are several references that are used in the literature to determine the relative position of band edges [33][34][35][36]. The average electrostatic potential is the best common reference but it is very expensive to calculate as both materials of interest must be contained within one common simulation cell.…”

Section: B Band Edge Alignmentmentioning

confidence: 99%

Band-Gap and Band-Edge Engineering of Multicomponent Garnet Scintillators from First Principles

Yadav¹,

Uberuaga²,

Nikl³

et al. 2015

Phys. Rev. Applied

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Complex doping schemes in RE3Al5O12 (RE=rare earth element) garnet compounds have recently led to pronounced improvements in scintillator performance. Specifically, by admixing lutetium and yttrium aluminate garnets with gallium and gadolinium, the band-gap was altered in a manner that facilitated the removal of deleterious electron trapping associated with cation antisite defects. Here, we expand upon this initial work to systematically investigate the effect of substitutional admixing on the energy levels of band edges. Density functional theory was used to survey potential admixing candidates that modify either the conduction band minimum (CBM) or valence band maximum (VBM). We considered two sets of compositions based on Lu3B5O12 where B = Al, Ga, In, As, and Sb; and RE3Al5O12, where RE = Lu, Gd, Dy, and Er. We found that admixing with various RE cations does not appreciably effect the band gap or band edges. In contrast, substituting Al with cations of dissimilar ionic radii has a profound impact on the band structure. We further show that certain dopants can be used to selectively modify only the CBM or the VBM. Specifically, Ga and In decrease the band gap by lowering the CBM, while As and Sb decrease the band gap by raising the VBM. These results demonstrate a powerful approach to quickly screen the impact of dopants on the electronic structure of scintillator compounds, identifying those dopants which alter the band edges in very specific ways to eliminate both electron and hole traps responsible for performance limitations. This approach should be broadly applicable for the optimization of electronic and optical performance for a wide range of compounds by tuning the VBM and CBM.

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Section: B Band Edge Alignmentmentioning

confidence: 99%

Band-Gap and Band-Edge Engineering of Multicomponent Garnet Scintillators from First Principles

Yadav¹,

Uberuaga²,

Nikl³

et al. 2015

Phys. Rev. Applied

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“…In this respect, it is of utmost importance to assess the changes induced by OH vac in terms of both local and global polarizations across the tube section. Following [24], the change (∆V ) in the (microscopically) averaged electrostatic potential across the polarized interface can be related to the electrostatic dipole across the interface itself (µ) as ∆V = eµ/ǫ 0 . On this basis, it is straightforward to evaluate the actual dipole moment across the tube walls from ∆V values calculated in DFT.…”

Section: Figmentioning

confidence: 99%

Hydroxyl vacancies in single-walled aluminosilicate and aluminogermanate nanotubes

Teobaldi

Beglitis

Fisher

et al. 2009

J. Phys.: Condens. Matter

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We report the first theoretical study of hydroxyl vacancies in aluminosilicate and aluminogermanate single-walled metal-oxide nanotubes. The defects are modeled on both sides of the tube walls and lead to occupied and empty states in the band gap which are highly localized both in energy and in real space. We find different magnetization states depending on both the chemical composition and the specific side with respect to the tube cavity. The defect-induced perturbations to the pristine electronic structure are related to the electrostatic polarization across the tube walls and the ensuing change in Brønsted acid-base reactivity. Finally, the capacity to counterbalance local charge accumulations, a characteristic feature of these systems, is discussed in view of their potential application as insulating coatings for one-dimensional conducting nanodevices.

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“…Note that the lateral dimension of the heterostructure happens to coincide with the average of the WZ and ZB lattice parameters. The valence band offset of the ZB and WZ segments can be computed 45 as…”

mentioning

confidence: 99%

As vacancies, Ga antisites, and Au impurities in zinc blende and wurtzite GaAs nanowire segments from first principles

Du¹,

Sakong²,

Kratzer³

2013

Phys. Rev. B

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In this paper some specific issues related to point defects in GaAs nanowires are addressed with the help of density functional theory calculations. These issues mainly arise from the growth of nanowires under conditions different from those used for thin films or bulk GaAs, such as the co-existence of zincblende and wurtzite polytypes, the use of gold particles as catalyst, and the arsenic-limited growth regime. Hence, we carry out density-functional calculations for As vacancies, GaAs antisites, and Au impurities in ZB and WZ GaAs crystals. Our results show that As vacancies can diffuse within in a ZB GaAs crystal with migration barriers of ∼1.9 eV. Within WZ GaAs, As vacancy diffusion is found to be anisotropic, with low barriers of 1.60 up to 1.79 eV (depending on doping conditions) in the ab-plane, while there are higher barriers of 2.07 to 2.44 eV to diffuse along the c-axis. The formation energy of Au impurities is found to be generally much lower than those of arsenic vacancies or GaAs antisites. Thus, Au impurities will be the dominant defects formed in Au-catalyzed nanowire growth. Moreover, we find that it is energetically more favorable by 1 to 2 eV for an Au impurity to replace a lattice Ga atom than a lattice As atom in GaAs. An Au substitutional defect for a lattice Ga atom in ZB GaAs is found to create a charge transfer level in the lower half of the band gap. While our calculations locate this level at Ev + 0.22 eV, taking into account the inaccuracy of the density functional that ought to be corrected by a downshift of Ev by about 0.2 eV results in good agreement with the experimental result of Ev + 0.4 eV.

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Heterojunction band offset engineering

Cited by 448 publications

References 291 publications

Band-Gap and Band-Edge Engineering of Multicomponent Garnet Scintillators from First Principles

Band-Gap and Band-Edge Engineering of Multicomponent Garnet Scintillators from First Principles

Hydroxyl vacancies in single-walled aluminosilicate and aluminogermanate nanotubes

As vacancies, Ga antisites, and Au impurities in zinc blende and wurtzite GaAs nanowire segments from first principles

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