Fermi-level pinning through defects at GaAs/oxide interfaces: A density functional study

Colleoni, Davide; Miceli, Giacomo; Pasquarello, Alfredo

doi:10.1103/physrevb.92.125304

Cited by 31 publications

(23 citation statements)

References 87 publications

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“…For this configuration, the CTLs are found to be e þ2=þ1 ¼ À0:06 eV relative to the VBM and e þ1=0 ¼ 0.43 eV relative the CBM, or in other words, within the valence and conduction bands, respectively, and do not give rise to states in the semiconductor bandgap. This result for the e þ1=0 level is in contrast to previous calculations of the As Ga antisite near the oxide in a model of the GaAs/ Al 2 O 3 interface 43 calculated within a hybrid DFT framework, which exhibited little difference to the corresponding CTLs of the bulk AsGa antisite. The discrepancy may be ascribed to a combination of factors including that the wide GaAs bandgap may result in significantly less hybridization between the band edges and the respective charged defect states compared to the narrower bandgap In 0.53 Ga 0.…”

Section: Ctls For Surface Defectscontrasting

confidence: 99%

“…Interfacial bonding with O atoms bonding directly to a Ga in turn bonded to an As atom about the antisite is studied in Ref. 43, whereas the metal (Al) atoms of the oxide are bonding directly to As atoms at the semiconductor surface in the model used in this study, which are in turn bonding to the As atom corresponding to the antisite. The local chemical environment in Ref.…”

Section: Ctls For Surface Defectsmentioning

confidence: 99%

“…The local chemical environment in Ref. 43, in this sense, is more "bulk-like" and the differences highlight how significantly differing electrical properties arise from differences in the local chemical environment of a defect. The shift in the CTLs between the bulkand the As Ga configuration occurring near the interfacial layer is found to be significantly smaller than the CTL shifts for the bulk-and surface-model of the Ga As antisite bonding directly to the oxide; the latter sites have a different local chemistry due to the bonding mechanism to oxide atoms, and hence, the larger associated differences in the CTLs relative to bulk defects are not unexpected.…”

Section: Ctls For Surface Defectsmentioning

confidence: 99%

“…Hence, although the growth conditions are described as "Asrich," small variations in the growth conditions can lead to either "As-rich" or "In/Ga-rich" conditions at the growth front, hence the possibility of forming either or both As Ga and Ga As antisites during the growth of In 0.57 Ga 0. 43 As.…”

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confidence: 99%

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First principles modeling of defects in the Al2O3/In0.53Ga0.47As system

Greene‐Diniz¹,

Kuhn

Hurley³

et al. 2017

Journal of Applied Physics

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Density functional theory paired with a first order many-body perturbation theory correction is applied to determine formation energies and charge transition energies for point defects in bulk In0.53Ga0.47As and for models of the In0.53Ga0.47As/Al2O3 interface. The results are consistent with previous computational studies that AsGa antisites are candidates for defects observed in capacitance voltage measurements on metal-oxide-semiconductor capacitors, as the AsGa antisite introduces energy states near the valence band maximum and near the middle of the energy band gap. However, substantial broadening in the distribution of the GaAs charge transition levels due to the variation in the local chemical environment resulting from alloying on the cation (In/Ga) sublattice is found, whereas this effect is absent for AsGa antisites. Also, charge transition energy levels are found to vary based on proximity to the semiconductor/oxide interface. The combined effects of alloy-and proximity-shift on the GaAs antisite charge transition energies are consistent with the distribution of interface defect levels between the valence band edge and midgap as extracted from electrical characterization data. Hence, kinetic growth conditions leading to a high density of either GaAs or AsGa antisites near the In0.53Ga0.47As/Al2O3 interface are both consistent with defect energy levels at or below midgap.Hence the purpose of the calculations presented in this study is to narrow the possible set of atomistic configurations giving rise to defects levels in the band gap, and thereby motivate the development of growth conditions and processing steps that either passivate the defects or avoid their formation.Recent density functional theory (DFT) investigations of defects in related III-V (GaAs, InAs, and InGaAs alloys) materials have been reported. These studies provide predictions for the stability and amphoteric nature of native defects in bulk and oxide-terminated surface models using hybrid exchange-correlation (XC) functionals [10-14], with the hybrid functionals chosen to overcome the DFT band gap problem. In such approaches a fraction a of Hartree-Fock exchange is mixed into the XC functional (giving rise to a hybrid functional), and the value of a is usually adjusted to reproduce the experimental band gap. These authors [10][11][12][13][14] conclude that the position of the midgap charge transition levels (CTLs) of the AsGa antisite, combined with a predicted lower formation energy relative to other commonly studied point defects, , suggest that this antisite is responsible for the midgap Dit states observed in the capacitance-voltage (CV) response of In0.53Ga0.47As/high-k oxide MOS capacitors. In other works, studies of bonding mechanisms at the III-V/oxide interfaces GaAs/Al2O3 and GaAs/HfO2 have been presented [15], and predictions of charge transition levels (CTLs) of As and P vacancies at (110) oriented GaAs and InP surfaces are reported in ref. [16]. The latter utilizes many body perturbation theory (MBPT) to avoid the need to...

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Section: Ctls For Surface Defectscontrasting

confidence: 99%

Section: Ctls For Surface Defectsmentioning

confidence: 99%

Section: Ctls For Surface Defectsmentioning

confidence: 99%

mentioning

confidence: 99%

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First principles modeling of defects in the Al2O3/In0.53Ga0.47As system

Greene‐Diniz¹,

Kuhn

Hurley³

et al. 2017

Journal of Applied Physics

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“…24,25 This scheme preserves the overall accuracy of hybrid functional calculations, [26][27][28][29][30] but significantly reduces the computational cost, thereby making possible the study of a large variety of defect positions within a disordered alloy, such as In 0.17 Al 0.83 N. To illustrate the accuracy of this scheme in the case of III-V compounds, we focused on the O N impurity in AlN. In agreement with previous studies, 13,31-33 we found that the defect is only stable in the singly positive and singly negative charge states, the latter being particularly stabilized by a displacement of the O atom out of the regular lattice site.…”

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confidence: 99%

Oxygen DX center in In0.17Al0.83N: Nonradiative recombination and persistent photoconductivity

Meli

Miceli

Pasquarello

2017

Applied Physics Letters

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Using a hybrid density-functional scheme, we address the O impurity substitutional to N (O N ) in In 0.17 Al 0.83 N. Our modelling supports In clustering to account for the strong band-gap bowing observed in In x Al 1-x N alloys. To study the O N defect in In 0.17 Al 0.83 N alloys, we therefore consider a model containing an In cluster and find that the most stable configuration shows four In nearest neighbors. We show that such a O N defect forms a DX center and gives rise to two defect levels at 0.70 and 0.41 eV below the conduction band edge, in good agreement with experiment. The calculated defect energetics entail a fast nonradiative recombination upon photoexcitation at room temperature and account for the observation of persistent photoconductivity at low temperature.PACS numbers: 71.55. Eq,61.72.uj In the last decades, In x Al 1-x N has attracted a great deal of interest for its possible applications in electronic and optoelectronic devices. 1-3 In particular, In 0.17 Al 0.83 N is nearly lattice matched to GaN and can be used to realize strain-free heterostructures. 4,5 Applications include distributed Bragg reflectors, thick cladding layers in edge emitting lasers, waveguides exploiting the large difference in refractive indices between InAlN and GaN, and high-electron mobility transistors (HEMTs). [6][7][8] To control the electronic properties of these materials, it is important to understand the role of impurities. Upon growth through metalorganic vapor phase epitaxy (MOVPE), it is known that considerable concentrations of oxygen and carbon impurities are incorporated. 8 Experimental investigations have identified various defect states with activation energies ranging between 200 and 500 meV. 9-11 However, their origin has been difficult to ascertain and it has remained unclear whether these states relate to point defects or to dislocations. More recently, defect states have been measured at 68 meV and 270 meV and tentatively assigned to oxygen on the basis of their concentration. 12 The observation of persistent photoconductivity (PPC) effects has been taken as an indication supporting this interpretation, 12 as oxygen is known to give rise to DX centers in AlN. 13 In this Letter, we study the oxygen impurity substitutional to nitrogen (O N ) in In 0.17 Al 0.83 N through densityfunctional-theory calculations. We find that O N gives defect levels that are in agreement with experimental observations. These impurities behave like DX centers and can explain the origin of the persistent photoconductivity effects.In our calculations, we make use of the semilocal density functional introduced by Perdew, Burke, and Ernzerhof (PBE), 14 and of the hybrid functional introduced by Heyd, Scuseria, and Ernzerhof (HSE). 15,16 In the latter, the fraction of Fock exchange is set to α = 0.37 for AlN and to α = 0.19 for InN, in order to reproduce their experimental band gaps. For intermediate In x Al 1-x N alloys, the mixing coefficient α is linearly interpolated.We use normconserving pseudopotentials to treat corev...

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Decreasing Defect‐State Density of Al₂O₃/Ga_xIn₁₋_xAs Device Interfaces with InO_x Structures

Mäkelä

Tuominen

Dahl

et al. 2017

Adv Materials Inter

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Control of defect densities at insulator/GaxIn1−xAs interfaces is essential for optimal operation of various devices like transistors and infrared detectors to suppress, for example, nonradiative recombination, Fermi‐level pinning, and leakage currents. It is reported that a thin InOx interface layer is useful to limit the formation of these defects by showing effect of InOx on quantum efficiency of Ga0.45In0.55As detector and on photoluminescence of GaAs. A study of the Al2O3/GaAs interface via hard X‐ray synchrotron photoelectron spectroscopy reveals chemical structure changes at the interface induced by this beneficial InOx incorporation: the InOx sheet acts as an O diffusion barrier that prevents oxidation of GaAs and concomitant As bond rupture.

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Fermi-level pinning through defects at GaAs/oxide interfaces: A density functional study

Cited by 31 publications

References 87 publications

First principles modeling of defects in the Al2O3/In0.53Ga0.47As system

First principles modeling of defects in the Al2O3/In0.53Ga0.47As system

Oxygen DX center in In0.17Al0.83N: Nonradiative recombination and persistent photoconductivity

Decreasing Defect‐State Density of Al₂O₃/Ga_xIn₁₋_xAs Device Interfaces with InO_x Structures

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Fermi-level pinning through defects at GaAs/oxide interfaces: A density functional study

Cited by 31 publications

References 87 publications

First principles modeling of defects in the Al2O3/In0.53Ga0.47As system

First principles modeling of defects in the Al2O3/In0.53Ga0.47As system

Oxygen DX center in In0.17Al0.83N: Nonradiative recombination and persistent photoconductivity

Decreasing Defect‐State Density of Al2O3/GaxIn1−xAs Device Interfaces with InOx Structures

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Decreasing Defect‐State Density of Al₂O₃/Ga_xIn₁₋_xAs Device Interfaces with InO_x Structures