Electronic Defects in Amorphous Oxide Semiconductors: A Review

Ide, Keisuke; Nomura, Kenji; Hosono, Hideo; Kamiya, Toshio

doi:10.1002/pssa.201800372

Cited by 201 publications

(210 citation statements)

References 140 publications

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“…1(a). The subgap state densities and VB Urbach tail parameters in Table I are similar to values reported from various experimental techniques [7,21,[38][39][40][41][42][43]. These previous measurements are typically limited to characterizing either shallow states near the CBM or deep states near the VBM, whereas the DOS profile obtained from UBPC extends continuously from 0.3 to TABLE I. a-IGZO DOS figures of merit.…”

Section: Resultssupporting

confidence: 71%

“…Amorphous In-Ga-Zn-O (a-IGZO) in particular has become a successful alternative to amorphous silicon for manufacturing TFTs with high mobility [5] and low leakage current [6], enabling large-area display applications. In a-IGZO, subtle variations in composition or processing create subgap defect and vacancy states [7][8][9][10][11][12] that control both TFT semiconducting behavior [13] and performance limitations [14]. The ability to measure and identify the structural origins of these subgap states is crucial to understanding the electrical behavior of a-IGZO TFTs.…”

Section: Introductionmentioning

confidence: 99%

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Ultrabroadband density of states of amorphous In-Ga-Zn-O

Vogt

Malmberg

Buchanan

et al. 2020

Phys. Rev. Research

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The subgap density of states of amorphous indium gallium zinc oxide (a-IGZO) is obtained using the ultrabroadband photoconduction response of thin-film transistors (TFTs). Density-functional theory simulations classify the origin of the measured subgap density of states peaks as a series of donorlike oxygen vacancy states and acceptorlike Zn vacancy states. Donor peaks are found both near the conduction band and deep in the subgap, with peak densities of 10 17 −10 18 cm −3 eV −1. Two deep acceptorlike peaks lie adjacent to the valance-band Urbach tail region at 2.0-2.5 eV below the conduction-band edge, with peak densities in the range of 10 18 cm −3 eV −1. By applying detailed charge balance, we show that increasing the deep acceptor density strongly shifts the a-IGZO TFT threshold voltage to more positive values. Photoionization (hν > 2.0 eV) of deep acceptors is one cause of transfer curve hysteresis in a-IGZO TFTs, owing to longer recombination lifetimes as electrons are captured into acceptorlike vacancies.

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Section: Resultssupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Ultrabroadband density of states of amorphous In-Ga-Zn-O

Vogt

Malmberg

Buchanan

et al. 2020

Phys. Rev. Research

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“…Defect engineering has been one of the core strategies in controlling oxide semiconductor properties. [302][303][304] Here we will take some representative oxide semiconductors (ZnO, In 2 O 3 , IGZO) as examples, to discuss how the control of defects, such as V O , V C and interstitials, could help to shape materials and devices.…”

Section: Wide Bandgap Oxide Semiconductorsmentioning

confidence: 99%

“…298,[352][353][354][355] Defects have a significant influence on a-IGZO materials and TFTs, i.e., while most defects are detrimental to device performance, some defects actually play a positive role in improving carrier density. 304,356,357 V O , metal-metal bonds and H incorporation are the three main defect types present in channel region of a-IGZO TFTs. 358 V O could participate in several different local coordination structures: (i) 'Corner-share' structure formed by V O coordinated with small numbers of cations, (ii) 'Free space' structure formed by V O adjacent to a large open space and (iii) 'Edge/Face-sharing' structure formed by V O surrounded by many cations, as shown in Fig.…”

Section: Wide Bandgap Oxide Semiconductorsmentioning

confidence: 99%

Defects in complex oxide thin films for electronics and energy applications: challenges and opportunities

et al. 2020

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“…[ 4–6 ] Optical transparency over 80%, a result of wide band gaps (>3 eV), is another benefit of AOSs, enabling transparent electronics. [ 7–9 ]…”

Section: Introductionmentioning

confidence: 99%

Origin of p‐Type Conduction in Amorphous CuI: A First‐Principles Investigation

Lee

Youn

Jeong

et al. 2020

Physica Status Solidi (b)

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Recently, Jun et al. (Adv. Mater. 2018, 30, 1706573) reported Sn‐doped amorphous phases of CuI (a‐CuI) as a new class of transparent p‐type semiconductors. It is surprising that high mobilities are found despite amorphous structures tend to localize carriers, particularly the directional p orbitals of anions. To reveal the microscopic origin of the new p‐type amorphous semiconductors, density functional theory calculations are performed, and structural and electrical properties of a‐CuI are investigated. Amorphous models from melt‐quench simulations consist of structural motifs that resemble local orders in crystalline polymorphs of CuI. Despite the absence of translational symmetry, states at valence band maximum (VBM) are substantially extended in linear ways due to the hybridization between I‐5p states, explaining the high hole mobilities in the experiment. Sn‐doped a‐CuI is also investigated and it is found that Sn atoms stabilize the amorphous structure without disturbing the hole transport. Furthermore, results on nonstoichiometric models show that Cu‐deficiency increases the hole concentration in a‐CuI and also enhances the delocalization of VBM states, which is consistent with the experimental observation that the hole mobility increases with doping concentrations. Herein, the origin of hole conduction in amorphous CuI is enlightened, which is believed to contribute in the development of high‐performance p‐type amorphous materials.

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Electronic Defects in Amorphous Oxide Semiconductors: A Review

Cited by 201 publications

References 140 publications

Ultrabroadband density of states of amorphous In-Ga-Zn-O

Ultrabroadband density of states of amorphous In-Ga-Zn-O

Defects in complex oxide thin films for electronics and energy applications: challenges and opportunities

Origin of p‐Type Conduction in Amorphous CuI: A First‐Principles Investigation

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