Trap-limited and percolation conduction mechanisms in amorphous oxide semiconductor thin film transistors

Lee, Sungwon; Ghaffarzadeh, Khashayar; Nathan, Arokia; Robertson, John; Jeon, Sanghun; Kim, Changjung; Song, Ihun; Chung, U‐In

doi:10.1063/1.3589371

Cited by 265 publications

(227 citation statements)

References 17 publications

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“…As expected, structural disorder increases with the substitution level in ternary and quaternary AOSs; however, there is no clear understanding regarding the role played by the individual metal species in the formation of amorphous state and the AOSs properties. Most research has focused on quaternary oxides such as a-In-Ga-Zn-O or a-Zn-In-Sn-O given their technological appeal; [48,49,[51][52][53][54][55][56][57][62][63][64][65][66]68,69,73,74,76] only a few studies addressed the properties of ternary AOSs systematically. [67,85,86] Moreover, a comparison of the results available in the literature is likely to be inconclusive because the crystallization temperature depends strongly not only on the metal composition but also on growth conditions (such as oxygen partial pressure, postdeposition temperatures and times) as well as film thickness.…”

Section: Local Structure and Amorphization Efficiencymentioning

confidence: 99%

“…The research area of transparent conducting oxides (TCOs) dates back to 1907 when CdO was reported to combine both optical transparency in the visible range and good electrical of amorphous indium oxide appeared in 2009, [61] followed by models of electron transport in multi-cation AOSs, [62][63][64][65][66][67] DFT calculations of defect formation, [68][69][70][71][72][73][74][75] and statistical descriptions of amorphous network. [76][77][78] However, several key questions regarding the nanostructure and morphology, crystallization, carrier generation, and conductivity mechanisms in AOSs remain unanswered and require a unified theoretical framework capable of handling all these aspects in tandem.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Recent Advances in Understanding the Structure and Properties of Amorphous Oxide Semiconductors

Medvedeva

Buchholz

Chang

2017

Adv Elect Materials

137

144

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conductivity. [1] Following the discovery of SnO 2 with a similar unique combination of properties, [2] several patents were filed in the 1940s to employ TCOs as antistatic coatings and transparent heaters-long before the discovery of the now well-known Sn-doped In 2 O 3 (ITO) and Al-doped ZnO, [3] widely employed as flat panel display electrodes in the past decades. Despite great technological demand for TCOs [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and extensive experimental efforts to improve the conductivity via impurity doping, [21,22] to tune the work function and carrier concentration via cation composition, [23][24][25][26][27][28] to achieve two-dimensional transport via heterointerfaces, [29] and to p-dope the oxides toward active layers of transparent electronics, [30][31][32] theoretical understanding of these fascinating materials has lagged behind significantly. The first electronic band structure of ITO was calculated in 2001; [33] the role of native defects in prototype TCOs was understood after 2002; [34][35][36][37] the properties of multi-cation TCOs were first considered in 2004 [37][38][39][40][41][42] followed by modeling of novel TCO hosts [43,44] and spin-dependent transport in transition-metal-doped TCOs; [45] the nature of the band gap in In 2 O 3 was clarified in 2008; [46] and a first highthroughput search for p-type TCOs was performed in 2013. [47] Complex oxides that consist of multiple post-transition metals, such as InGaZnO 4 , have recently become competitive with silicon as the active transistor layer to drive arrays of pixels in large area displays. [9,[13][14][15][16][17][18][19]24] As the billion-dollar display industry moves forward, the amorphous phase of the complex oxides is favored both for flexible and high-resolution display applications. [13][14][15][16][48][49][50][51][52][53][54][55][56][57][58][59] The unique properties of AOSs were first demonstrated in 1990, [60] and the research area has been growing exponentially since then. Unlike Si-based semiconductors, AOSs were shown to exhibit optical, electrical, thermal, and mechanical properties that are comparable or even superior to those possessed by their crystalline counterparts. [48][49][50][51][52][53][54][55][56][57][58] Table 1 summarizes the key physical properties of best-performing crystalline TCOs and AOSs; the differences (or the lack thereof) between the two will be discussed in detail in the respective sections below.

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Section: Local Structure and Amorphization Efficiencymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Recent Advances in Understanding the Structure and Properties of Amorphous Oxide Semiconductors

Medvedeva

Buchholz

Chang

2017

Adv Elect Materials

137

144

View full text Add to dashboard Cite

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“…Thin-film transistors are good examples: the mobility is affected by band tailing [2], although the band-tail-state effect on carrier transport is strongly material dependent [3]. Band tails are also known to reduce the efficiency of solar cells [4,5] and to be the limiting factor in the case of amorphous Si solar cells [6].…”

Section: Introductionmentioning

confidence: 99%

Absorption Coefficient of a Semiconductor Thin Film from Photoluminescence

et al. 2018

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The photoluminescence (PL) of semiconductors can be used to determine their absorption coefficient (α) using Planck's generalized law. The standard method, suitable only for self-supported thick samples, like wafers, is extended to multilayer thin films by means of the transfer-matrix method to include the effect of the substrate and optional front layers. α values measured on various thin-film solar-cell absorbers by both PL and photothermal deflection spectroscopy (PDS) show good agreement. PL measurements are extremely sensitive to the semiconductor absorption and allow us to advantageously circumvent parasitic absorption from the substrate; thus, α can be accurately determined down to very low values, allowing us to investigate deep band tails with a higher dynamic range than in any other method, including spectrophotometry and PDS.

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“…22 The electron conduction in a-IGZO is proposed by percolation conduction theory, where the electrons need to pass through the Gaussian distribution of energy barriers with an average barrier height of 50meV. 21,23 These barriers are originated by the disorder of Ga + /Zn + cations, which make the Gaussian type distribution around E C in amorphous IGZO. 21 The negative temperature coefficient of µ sat observed for positive V TG (shown in Fig.…”

Section: -4mentioning

confidence: 99%

Semiconductor to metallic transition in bulk accumulated amorphous indium-gallium-zinc-oxide dual gate thin-film transistor

2015

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We investigated the effects of top gate voltage (VTG) and temperature (in the range of 25 to 70 oC) on dual-gate (DG) back-channel-etched (BCE) amorphous-indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs) characteristics. The increment of VTG from -20V to +20V, decreases the threshold voltage (VTH) from 19.6V to 3.8V and increases the electron density to 8.8 x 1018cm−3. Temperature dependent field-effect mobility in saturation regime, extracted from bottom gate sweep, show a critical dependency on VTG. At VTG of 20V, the mobility decreases from 19.1 to 15.4 cm2/V ⋅ s with increasing temperature, showing a metallic conduction. On the other hand, at VTG of - 20V, the mobility increases from 6.4 to 7.5cm2/V ⋅ s with increasing temperature. Since the top gate bias controls the position of Fermi level, the temperature dependent mobility shows metallic conduction when the Fermi level is above the conduction band edge, by applying high positive bias to the top gate.

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Trap-limited and percolation conduction mechanisms in amorphous oxide semiconductor thin film transistors

Cited by 265 publications

References 17 publications

Recent Advances in Understanding the Structure and Properties of Amorphous Oxide Semiconductors

Recent Advances in Understanding the Structure and Properties of Amorphous Oxide Semiconductors

Absorption Coefficient of a Semiconductor Thin Film from Photoluminescence

Semiconductor to metallic transition in bulk accumulated amorphous indium-gallium-zinc-oxide dual gate thin-film transistor

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