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

Vogt, Kyle T.; Malmberg, Christopher E.; Buchanan, Jacob C.; Mattson, George W.; Brandt, G. Mirek; Fast, Dylan B.; Cheong, Paul Ha‐Yeon; Wager, John F.; Graham, Mary

doi:10.1103/physrevresearch.2.033358

Cited by 13 publications

(12 citation statements)

References 65 publications

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“…Since the excellent electron transport properties, IGZO films are more suitable for TFT applications. 27,28 In QLED, the carrier injection is usually unbalanced. The excess electron will cause serious nonradiative (Auger) recombination and quenching the exciton.…”

Section: Resultsmentioning

confidence: 99%

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Patterning of quantum dot light‐emitting diodes based on IGZO films

Jia

et al. 2022

J Soc Info Display

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The patterning of quantum dot light-emitting diodes (QLED) is essential for QLED in the display application. In the work, we studied patterning thin film to form IGZO electron transport layers for QLED. Making use of a staggered IGZO film as the electron transport layer, we studied QLED degradation and observed luminance inversion, which is due to the non-uniform current spreading effect caused by the staggered IGZO film. The current crowding at the thinner film area (with lower electric resistance) leads to a patterned emission of the device but also a faster device degradation at the same time.

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Section: Resultsmentioning

confidence: 99%

“…Since the excellent electron transport properties, IGZO films are more suitable for TFT applications 27,28 . In QLED, the carrier injection is usually unbalanced.…”

Section: Resultsmentioning

confidence: 99%

Patterning of quantum dot light‐emitting diodes based on IGZO films

Jia

et al. 2022

J Soc Info Display

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“…In traditional semiconductors such as silicon, doping is achieved by atomic substitution with elements from neighboring columns in the periodic table. Doping in IGZO is associated with a mechanism of a different kind, in which the main source of electron doping arises from either interstitial hydrogen or oxygen vacancies. − These doping mechanisms make the integration of IGZO in devices very challenging due to the omnipresence of hydrogen sources and oxygen-scavenging layers in conventional CMOS process conditions. In this paper, we focus on the resilience of different phases of IGZO to the formation of oxygen vacancies.…”

Section: Introductionmentioning

confidence: 99%

Oxygen Defect Stability in Amorphous, C-Axis Aligned, and Spinel IGZO

Setten

Dekkers

Ključar

et al. 2021

ACS Appl. Electron. Mater.

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Good control of the doping concentration and profile in the active layer of a transistor is paramount to achieve optimal device reliability and electrical performance. For nonconventional semiconductors such as InGaZnO 4 (IGZO), the doping mechanisms and the factors impacting them need to be rediscovered to achieve this control. In IGZO, an important doping mechanism is the formation of oxygen defects. In this work, we map the stability of oxygen defects in IGZO as a function of the defect concentration for three different phases: amorphous, C-axis aligned, and spinel IGZO. By means of a detailed analysis of the evolution of the metal coordination in the three phases, we rationalize the observed similarities and differences. This insight enables us to estimate the doping concentration caused by oxygen scavenging by different contact metals, liner materials, and hydrogen sources introduced during the integration of the material in a transistor flow. From a study of the contact resistance in the Ohmic, high carrier density contact regime, we obtain a lower bound to the contact resistance. We learn that the different carrier concentrations, caused by the variations in oxygen scavenging between contact metals, have a larger impact than the direct difference in contact resistance caused by the intrinsic electronic properties of metals.

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“…Four primary types of intrinsic subgap states exist in a-IGZO, i.e., conduction band tail states (acceptor states exponentially distributed below the conduction band mobility edge), valence band tail states (donor states exponentially distributed above the valence band mobility edge), oxygen vacancy states (donor states forming a series of Gaussian-like peaks in the upper portion of the a-IGZO band gap), and metal vacancy states (acceptor states giving Gaussian-like peaks in the lower portion of the a-IGZO band gap). 5,6 . Both types of band tail states and oxygen vacancy states are ubiquitous in a-IGZO, while ultrabroadband photoconduction (UBPC) assessment reveals that the concentration of metal vacancy states is quite variable, e.g., 10 16 − 10 17 cm −3 for the bottom-gate a-IGZO TFTs of Vogt et al 5 and negligibly small (i.e., < 10 16 cm −3 ) for the top-gate a-IGZO TFTs examined herein.…”

Section: Introductionmentioning

confidence: 99%

“…5,6 . Both types of band tail states and oxygen vacancy states are ubiquitous in a-IGZO, while ultrabroadband photoconduction (UBPC) assessment reveals that the concentration of metal vacancy states is quite variable, e.g., 10 16 − 10 17 cm −3 for the bottom-gate a-IGZO TFTs of Vogt et al 5 and negligibly small (i.e., < 10 16 cm −3 ) for the top-gate a-IGZO TFTs examined herein.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen incorporation into amorphous indium gallium zinc oxide thin-film transistors

Mattson,

Vogt,

Wager

et al. 2021

Preprint

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Within the subgap of amorphous oxide semiconductors like amorphous indium gallium zinc oxide (a-IGZO) are donor-like and acceptor-like states that control the operational physics of optically transparent thin-film transistors (TFTs). Hydrogen incorporation into the channel layer of a top-gate a-IGZO TFT exists as an electron donor that causes an observed negative shift in the drain current-gate voltage (I D − V G ) transfer curve turn-on voltage. Normally, hydrogen is thought to create shallow electronic states just below the conduction band mobility edge, with the donor ionization state controlled by equilibrium thermodynamics involving the position of the Fermi level with respect to the donor ionization energy. However, hydrogen does not behave as a normal donor as revealed by the subgap density of states (DoS) measured by the photoconduction response of top-gate a-IGZO TFTs to within 0.3 eV of the CBM edge. Specifically, the DoS shows a subgap peak above the valence band mobility edge growing at the same rate that I D − V G transfer curve measurements suggest that hydrogen was incorporated into the channel layer. Such hydrogen donor behavior in a-IGZO is anomalous and can be understood as follows: Non-bonded hydrogen ionization precedes its incorporation into the a-IGZO network as a bonded species. Ionized hydrogen bonds to a charged oxygen-on-an-oxygen-site anion, resulting in the formation of a defect complex denoted herein as,1− defect complex creates a spectrally-broad (∼0.3 eV FWHM) distribution of electronic states observed in the bandgap centered at 0.4 eV above the valence band mobility edge.

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

Cited by 13 publications

References 65 publications

Patterning of quantum dot light‐emitting diodes based on IGZO films

Patterning of quantum dot light‐emitting diodes based on IGZO films

Oxygen Defect Stability in Amorphous, C-Axis Aligned, and Spinel IGZO

Hydrogen incorporation into amorphous indium gallium zinc oxide thin-film transistors

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