Oxygen defects in amorphous Al2O3: A hybrid functional study

Guo, Zhang; Ambrosio, Francesco; Pasquarello, Alfredo

doi:10.1063/1.4961125

Cited by 45 publications

(58 citation statements)

References 53 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In order to improve understanding of these defects in a-Al 2 O 3 , the properties of oxygen vacancies at 11 defect sites in 10 geometry samples have been calculated and are presented here. The distribution In amorphous Al 2 O 3 only the +2 or neutral charge states of the oxygen vacancy are thermodynamically stable, as also observed by Guo et al 67 . The (+2/0) charge transition level lies, on average, 3.5 eV above the VBM and 2.0 eV below the CBM (see Fig.…”

Section: Charge Transition Levels and Energy Levels Of H Isupporting

confidence: 75%

See 1 more Smart Citation

The origin of negative charging in amorphous Al₂O₃ films: the role of native defects

et al. 2019

View full text Add to dashboard Cite

Amorphous aluminum oxide Al 2 O 3 (a-Al 2 O 3 ) layers grown by various deposition techniques contain a significant density of negative charges. In spite of several experimental and theoretical studies, the origin of these charges still remains unclear. We report the results of extensive Density Functional Theory (DFT) calculations of native defects -O and Al vacancies and interstitials, as well as H interstitial centers -in different charge states in both crystalline α-Al 2 O 3 and in a-Al 2 O 3 . The results demonstrate that both the charging process and the energy distribution of traps responsible for negative charging of a-Al 2 O 3 films [M. B. Zahid et al., IEEE Trans. Electron Devices 57, 2907 (2010)] can be understood assuming that the negatively charged O i and V Al defects are nearly compensated by the positively charged H i , V O and Al i defects in as prepared samples. Following electron injection, the states of Al i , V O or H i in the band gap become occupied by electrons and sample becomes negatively charged. The optical excitation energies from these states into the oxide conduction band agree with the results of exhaustive photo-depopulation spectroscopy (EPDS) measurements [M. B. Zahid et al., IEEE Trans. Electron Devices 57, 2907 (2010)]. This new understanding of the origin of negative charging of a-Al 2 O 3 films is important for further development of nanoelectronic devices and solar cells.

show abstract

Section: Charge Transition Levels and Energy Levels Of H Isupporting

confidence: 75%

“…In amorphous Al 2 O 3 only the +2 or neutral charge states of the oxygen vacancy are thermodynamically stable, as also observed by Guo et al 67 . The (+2/0) charge transition level lies, on average, 3.5 eV above the VBM and 2.0 eV below the CBM (see Fig.…”

Section: B Oxygen Vacanciessupporting

confidence: 74%

The origin of negative charging in amorphous Al₂O₃ films: the role of native defects

et al. 2019

View full text Add to dashboard Cite

show abstract

“…In contrast, charge carriers generated from localized states within the energy gap characteristic of amorphous oxides present poor mobility and are easily recombined. 38,39 Although the bandgap (BG) energy of amorphous Al 2 O 3 is reported at about 6.5 eV, 40 the current PEC analysis indicates evident photoresponses at sub-gap energies in the anodically grown barrier oxide layers. For wide bandgap semiconductors, such as Al 2 O 3 , 41 the observed photocurrents at energy levels below the expected bandgap energy typically originate from internal photoemission of e/h pairs from the metal Fermi level into in-gap states in the oxide layer, following the classical Fowler behavior.…”

Section: Afm-skpfm-mentioning

confidence: 73%

Substrate Purity Effect on the Defect Formation and Properties of Amorphous Anodic Barrier Al₂O₃

González‐Castaño

Döbeli

Araullo‐Peters

et al. 2018

J. Electrochem. Soc.

View full text Add to dashboard Cite

A comprehensive study concerning the effect of different Al metal substrate purities (i.e. 99.5 versus 99.99%) on the properties of amorphous anodic barrier Al 2 O 3 is presented. The experimental findings demonstrate that only tiny variations in the purity of the employed Al materials lead to different oxide growth rate, surface charge, structural defect and impurities content. Below the ionic recombination potential characterized by Scanning Kelvin Probe Force Microscopy, an increase of the anodizing voltage leads to an improvement of the oxide barrier properties. The larger growth rate exhibited by the higher purity Al substrate however indicates the formation of highly disordered and inhomogeneous barrier oxides. A combination of photoelectrochemical and photoluminescence spectroscopies was used to characterize structural defect concentration and confirmed the presence of significantly higher concentrations in the oxide grown on the purer Al substrates. FT-IR and RBS/ERDA results indicate that H and C species are incorporated from the electrolyte solution in the barrier oxides with higher H amounts detected in the oxide grown on the purer Al substrate.

show abstract

“…25,54 Since the Fermi energy lies within the semiconductor band gap during the oxide deposition, the MD is performed with the defects in their neutral charge state [cf. Fig.…”

Section: -35mentioning

confidence: 99%

Nature of electron trap states under inversion at In0.53Ga0.47As/Al2O3 interfaces

Colleoni

Pourtois

Pasquarello

2017

Applied Physics Letters

Self Cite

View full text Add to dashboard Cite

In and Ga impurities substitutional to Al in the oxide layer resulting from diffusion out of the substrate are identified as candidates for electron traps under inversion at In 0.53 Ga 0.47 As/Al 2 O 3 interfaces. Through density-functional calculations, these defects are found to be thermodynamically stable in amorphous Al 2 O 3 and to be able to capture two electrons in a dangling bond upon breaking bonds with neighboring O atoms. Through a band alignment based on hybrid functional calculations, it is inferred that the corresponding defect levels lie at ∼1 eV above the conduction band minimum of In 0.53 Ga 0.47 As, in agreement with measured defect densities. These results support the technological importance of avoiding cation diffusion into the oxide layer.The microelectronic industry is investigating high mobility semiconductors for replacing silicon as substrate material. Among the III-V compounds, the In x Ga 1−x As family has gathered large interest for application in n-type devices.1 In particular, the compound In 0.53 Ga 0.47 As (here referred to as InGaAs) has suitable electronic properties for microelectronic devices and can easily be grown onto InP substrates.1,2 Amorphous Al 2 O 3 is the preferred dielectric owing to its wide bandgap, high breakdown field, and high thermal stability. 2Several passivation procedures have been considered to reduce the high density of interfacial defect states occurring at III-V/oxide interfaces (D it ).3-7 The origin of these states has been for long debated and recently assigned to As-As dimer bonds. [8][9][10][11][12][13] In addition to these interfacial states, a high density of oxide traps (D ot ) has recently been detected in the oxide layer of metal-oxide-semiconductor (MOS) devices. Capacitancevoltage (CV) measurements show a bimodal distribution for the density of defect states in the oxide, 14 with one peak at 1.5 eV above and the other at 0.5 eV below the CBM of InGaAs. Similarly, through positive bias temperature instability (PBTI) experiments, a wide distribution of defect states centered at about 1 eV above the InGaAs conduction band maximum (CBM) has been inferred.15 These states are considered to be at the origin of the degradation of the electrical properties, thereby compromising the performance of the corresponding MOS devices.14,15 Indeed, upon reaching the inversion of carrier population, the Fermi energy is pushed deep into the conduction band of InGaAs in order to achieve high carrier concentrations, and is then susceptible to defects in the upper part of the oxide band gap. The atomic origin of these defects has remained elusive. A hint might come from electrical measurements on InGaAs/Al 2 O 3 and Ge/GeO x /Al 2 O 3 interfaces which yield similar field acceleration factors, 16 but an assessment concerning the nature of the involved defects remains out of reach on this basis. More indicatively, a) Electronic mail: davide.colleoni@epfl.ch time-of-flight secondary ion mass spectroscopy studies on GaAs/Al 2 O 3 and InGaAs/Al 2 O 3 interfaces revea...

show abstract

Oxygen defects in amorphous Al2O3: A hybrid functional study

Cited by 45 publications

References 53 publications

The origin of negative charging in amorphous Al₂O₃ films: the role of native defects

The origin of negative charging in amorphous Al₂O₃ films: the role of native defects

Substrate Purity Effect on the Defect Formation and Properties of Amorphous Anodic Barrier Al₂O₃

Nature of electron trap states under inversion at In0.53Ga0.47As/Al2O3 interfaces

Contact Info

Product

Resources

About

Oxygen defects in amorphous Al2O3: A hybrid functional study

Cited by 45 publications

References 53 publications

The origin of negative charging in amorphous Al2O3 films: the role of native defects

The origin of negative charging in amorphous Al2O3 films: the role of native defects

Substrate Purity Effect on the Defect Formation and Properties of Amorphous Anodic Barrier Al2O3

Nature of electron trap states under inversion at In0.53Ga0.47As/Al2O3 interfaces

Contact Info

Product

Resources

About

The origin of negative charging in amorphous Al₂O₃ films: the role of native defects

The origin of negative charging in amorphous Al₂O₃ films: the role of native defects

Substrate Purity Effect on the Defect Formation and Properties of Amorphous Anodic Barrier Al₂O₃