Properties and doping limits of amorphous oxide semiconductors

Robertson, John

doi:10.1016/j.jnoncrysol.2011.12.012

Cited by 39 publications

(34 citation statements)

References 66 publications

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“…As discussed in previous reviews , Fig. compares the density of states distribution of a‐IGZO to that of a‐Si:H , based on various estimates of the tail width and density of states (DOS) at the mobility edge . The slope of the conduction band tail may be slightly steeper than that of a‐Si:H. However, the main difference is that the DOS at the top of the mobility edge in an AOS is ∼10 18 cm −3 eV −1 , which is roughly 1000 times less than in a‐Si:H .…”

Section: Amorphous Oxide Semiconductorsmentioning

confidence: 96%

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Mott lecture: How bonding concepts can help understand amorphous semiconductor behavior

Robertson

2016

Physica Status Solidi (a)

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The article discusses how bonding concepts have allowed the development of amorphous semiconductors, in particular the 8−N rule of bonding, the doping mechanism in a‐Si:H, the weak effect of disorder on s states in amorphous oxide semiconductors, the strong effect of disorder on p states in amorphous carbon, and the effect of the change from resonant bonding to simple molecular covalent bonding in chalcogenide phase change materials.

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Section: Amorphous Oxide Semiconductorsmentioning

confidence: 96%

Section: Amorphous Oxide Semiconductorsmentioning

confidence: 99%

Mott lecture: How bonding concepts can help understand amorphous semiconductor behavior

Robertson

2016

Physica Status Solidi (a)

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“…6. This leads to a [20], [22], [28], [47]. downward band-bending at the front interface between gate-insulator and the IZO layer, aiding transfer of the generated electrons into the GIZO, while holes are localized at the front interface, as illustrated in Fig.…”

Section: A Sub-gap Optical Absorption and Oxygen Defectsmentioning

confidence: 99%

Transparent Semiconducting Oxide Technology for Touch Free Interactive Flexible Displays

et al. 2015

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This paper reviews the current status of the ubiquitous oxide semiconductor technology for flexible and transparent interactive displays.ABSTRACT | Amorphous oxide semiconductor thin film transistors and sensors constitute fundamental building blocks for a new generation of applications ranging from interactive displays and imaging to future electronic systems that are unconstrained by form factor. This makes the quest for high mobility materials processed at low temperatures even more compelling, to enable the layering of circuits and systems on plastic and possibly even paper substrates. Transparency is also an attractive feature that enables seamless embedding of electronics for the immersive ambient. This paper reviews the current status of the ubiquitous oxide semiconductor technology for flexible and transparent interactive displays, along with demonstrated examples of continuous thin film and nanowire systems for the transistor and sensor. Issues related to photosensing and active matrix operation are discussed along with solutions addressing the problem of threshold voltage instability and its compensation for fast recovery, particularly after light stress. Physics-based compact models for expedient design and simulation of analog and digital circuits are reviewed along with examples of key system building blocks. Finally we attempt to conceptualize a thin film transistor (TFT)-based fully heterogeneously integrated and autonomous system that can be realized using a combination of oxide and other technological routes. KEYWORDS | Active matrix organic light emitting diode (AMOLED); amorphous oxide semiconductors (AOS); interactive displays; nanowire transistors; oxygen defects; thin film transistors (TFTs) Manuscript

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“…61 In addition to the interface states, the defect tail states in the sub-band gap of the semiconductor (commonly expressed as Urbach energy) are known to affect TFT performance. 62 Using the photothermal deflection method, the Urbach energies of 98 and 102 meV are obtained for annealed films of ZTO (10% Sn) and ZTO (33% Sn), respectively. 63 These values are also very similar to previously reported Urbach energies $110 meV for ZTO 64 and $110-160 meV for IGZO.…”

Section: à2mentioning

confidence: 99%

Optimisation of amorphous zinc tin oxide thin film transistors by remote-plasma reactive sputtering

Niang

Cho

Heffernan

et al. 2016

Journal of Applied Physics

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The influence of the stoichiometry of amorphous zinc tin oxide (a-ZTO) thin films used as the semiconducting channel in thin film transistors (TFTs) is investigated. A-ZTO has been deposited using remote-plasma reactive sputtering from zinc:tin metal alloy targets with 10%, 33%, and 50% Sn at. %. Optimisations of thin films are performed by varying the oxygen flow, which is used as the reactive gas. The structural, optical, and electrical properties are investigated for the optimised films, which, after a post-deposition annealing at 500 °C in air, are also incorporated as the channel layer in TFTs. The optical band gap of a-ZTO films slightly increases from 3.5 to 3.8 eV with increasing tin content, with an average transmission ∼90% in the visible range. The surface roughness and crystallographic properties of the films are very similar before and after annealing. An a-ZTO TFT produced from the 10% Sn target shows a threshold voltage of 8 V, a switching ratio of 108, a sub-threshold slope of 0.55 V dec−1, and a field effect mobility of 15 cm2 V−1 s−1, which is a sharp increase from 0.8 cm2 V−1 s−1 obtained in a reference ZnO TFT. For TFTs produced from the 33% Sn target, the mobility is further increased to 21 cm2 V−1 s−1, but the sub-threshold slope is slightly deteriorated to 0.65 V dec−1. For TFTs produced from the 50% Sn target, the devices can no longer be switched off (i.e., there is no channel depletion). The effect of tin content on the TFT electrical performance is explained in the light of preferential sputtering encountered in reactive sputtering, which resulted in films sputtered from 10% and 33% Sn to be stoichiometrically close to the common Zn2SnO4 and ZnSnO3 phases.

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Properties and doping limits of amorphous oxide semiconductors

Cited by 39 publications

References 66 publications

Mott lecture: How bonding concepts can help understand amorphous semiconductor behavior

Mott lecture: How bonding concepts can help understand amorphous semiconductor behavior

Transparent Semiconducting Oxide Technology for Touch Free Interactive Flexible Displays

Optimisation of amorphous zinc tin oxide thin film transistors by remote-plasma reactive sputtering

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