Transition of dominant instability mechanism depending on negative gate bias under illumination in amorphous In-Ga-Zn-O thin film transistor

Oh, Himchan; Yoon, Sung‐Min; Ryu, Min Ki; Hwang, Chi‐Sun; Yang, Shinhyuk; Park, Sang‐Hee Ko

doi:10.1063/1.3540500

Cited by 86 publications

(59 citation statements)

References 15 publications

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“…10 Thin-film transistors made of amorphous oxide semiconductors exhibit a variety of metastable changes in their transistor characteristics through carrier doping and optical [11][12][13] or electrical [14][15][16][17][18][19][20][21] (or both [21][22][23][24][25][26][27][28] ) excitation of carriers. Indium (In)-based amorphous oxide semiconductors are considered as a promising material for next-generation thin-film electronics and optoelectronics because they have high electron mobility, transparency, flexibility and uniformity.…”

Section: Introductionmentioning

confidence: 99%

Undercoordinated indium as an intrinsic electron-trap center in amorphous InGaZnO4

Nahm

Kim

2014

NPG Asia Mater

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Undercoordinated indium (In*) is found to be an intrinsic defect that acts as a strong electron trap in amorphous InGaZnO 4 . Conduction electrons couple with the under-coordinated In* via Coulomb attraction, which is the driving force for the formation of an In*-M (M = In, Ga, or Zn) bond. The new structure is stable in the electron-trapped (2-) charge state, and we designate it as an intrinsic (In*-M) 2 − center in amorphous InGaZnO 4 . The (In*-M) 2 − centers are preferentially formed in heavily n-doped samples, resulting in a doping limit. They are also formed by electrical/optical stresses, which generate excited electrons, resulting in a metastable change in their electrical properties. NPG Asia Materials (2014) 6, e143; doi:10.1038/am.2014.103; published online 14 November 2014 INTRODUCTIONThe identification of charge-trapping defects on the atomic scale has been achieved in crystalline semiconductors. A donor can capture carrier electrons with large lattice relaxations, forming a DX (donor (D) deactivated (X)) center, 1-5 whereas an acceptor traps holes, forming an AX (acceptor (A) deactivated (X)) center. [5][6][7] However, in amorphous semiconductors, even though many charge-trapping phenomena that can modify electronic device characteristics 8 and be applied to nonvolatile memory devices 9 have been observed, the atomic and electronic structures of the charge-trapping defects lack clear understanding.Amorphous oxide semiconductors seriously suffer from chargetrapping events. 10 Thin-film transistors made of amorphous oxide semiconductors exhibit a variety of metastable changes in their transistor characteristics through carrier doping and optical [11][12][13] or electrical [14][15][16][17][18][19][20][21] (or both [21][22][23][24][25][26][27][28] ) excitation of carriers. Indium (In)-based amorphous oxide semiconductors are considered as a promising material for next-generation thin-film electronics and optoelectronics because they have high electron mobility, transparency, flexibility and uniformity. [29][30][31][32][33] However, the success of these applications has been limited by the lack of stability in their electrical properties owing to charge trapping.Investigation of the charge-trapping defects on the atomic scale is an essential prerequisite to overcome the instability issue of the indiumbased amorphous oxide semiconductors. An oxygen-vacancy (V O ) defect has been suggested as a metastable hole-trap center. 34,35 Unlike in crystalline oxides, V O and M-interstitial (M i ) (M = In, Ga, or Zn) are essentially indistinguishable in amorphous oxides. An M-M bond configuration can be understood as a V O and as anSimilarly, an O-O bond configuration can be interpreted as an M-vacancy (V M ) and as an In this paper, we find that undercoordinated indium (In*) acts as an intrinsic electron-trap center in In-based amorphous oxide semiconductors. Conduction electrons are subjected to a strong conductionelectron-ion interaction near the undercoordinated In* and trapped there, forming an In*-M bond. ...

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Section: Introductionmentioning

confidence: 99%

Undercoordinated indium as an intrinsic electron-trap center in amorphous InGaZnO4

Nahm

Kim

2014

NPG Asia Mater

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“…This means that the hole trapped charges during NBIS were de-trapped but the interface state charges were not detrapped under PBS. As previous report [4,12], the interface state charges are the donor-like states which are originated from the ionized oxygen vacancy, such as Vo + and Vo ++ . Since the donor-like states are placed at deep energy level and thus stable at room temperature, they are unlikely to recover under PBS without external excitation [4,12].…”

Section: Resultsmentioning

confidence: 88%

Investigation on stress induced hump phenomenon in IGZO thin film transistors under negative bias stress and illumination

Kim

Park

2015

Microelectronics Reliability

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“…1(d). At the V TG of À15 V, there is an $2.7 V negative shift, which gradually decreases to 0.42 V shift for V TG ¼ þ15 V. It clearly reveals the reduction of defect (ionization of oxygen vacancies/peroxide formation/oxygen interstitial) generation and/or hole trapping in IGZO bulk/ interfaces, 3,5,[7][8][9]22 by increasing V TG from À15 to þ15 V.…”

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confidence: 82%

“…With subgap light (<3.1 eV), the instability is dominated by the transition of valance band edge subgap states, through electron excitations. 3,5,[7][8][9] On the other hand, dual gate (principal gate is the bottom-gate (BG) and secondary gate is top-gate (TG)) dual driving (two gates are tied together during sweeping) structure with light shielded top gate metal (for example, Mo) suppress NBIS effects significantly for a-IGZO TFTs. 10 Dual gate (DG) dual driving a-IGZO TFTs show higher on-current (I on ), lower sub-threshold swing, and better uniformity, compared to SG a-IGZO TFTs.…”

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Effect of top gate bias on photocurrent and negative bias illumination stress instability in dual gate amorphous indium-gallium-zinc oxide thin-film transistor

Lee

Chowdhury

Park

et al. 2015

Applied Physics Letters

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We have studied the effect of top gate bias (VTG) on the generation of photocurrent and the decay of photocurrent for back channel etched inverted staggered dual gate structure amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film-transistors. Upon 5 min of exposure of 365 nm wavelength and 0.7 mW/cm2 intensity light with negative bottom gate bias, the maximum photocurrent increases from 3.29 to 322 pA with increasing the VTG from −15 to +15 V. By changing VTG from negative to positive, the Fermi level (EF) shifts toward conduction band edge (EC), which substantially controls the conversion of neutral vacancy to charged one (VO → VO+/VO2+ + e−/2e−), peroxide (O22−) formation or conversion of ionized interstitial (Oi2−) to neutral interstitial (Oi), thus electron concentration at conduction band. With increasing the exposure time, more carriers are generated, and thus, maximum photocurrent increases until being saturated. After negative bias illumination stress, the transfer curve shows −2.7 V shift at VTG = −15 V, which gradually decreases to −0.42 V shift at VTG = +15 V. It clearly reveals that the position of electron quasi-Fermi level controls the formation of donor defects (VO+/VO2+/O22−/Oi) and/or hole trapping in the a-IGZO /interfaces.

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Transition of dominant instability mechanism depending on negative gate bias under illumination in amorphous In-Ga-Zn-O thin film transistor

Cited by 86 publications

References 15 publications

Undercoordinated indium as an intrinsic electron-trap center in amorphous InGaZnO4

Undercoordinated indium as an intrinsic electron-trap center in amorphous InGaZnO4

Investigation on stress induced hump phenomenon in IGZO thin film transistors under negative bias stress and illumination

Effect of top gate bias on photocurrent and negative bias illumination stress instability in dual gate amorphous indium-gallium-zinc oxide thin-film transistor

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