Universal dependence on the channel conductivity of the competing weak localization and antilocalization in amorphous InGaZnO₄thin-film transistors

Abstract

We investigate the gate-voltage dependence of the magnetoconductivity of several amorphous InGaZnO4 (a-IGZO) thin-film transistors (TFTs). The magnetoconductivity exhibits gate-voltagecontrolled competitions between weak localization (WL) and weak antilocalization (WAL), and the respective weights of WL and WAL contributions demonstrate an intriguing universal dependence on the channel conductivity regardless of the difference in the electrical characteristics of the a-IGZO TFTs. Our findings help build a theoretical interpretation of the competing WL and WAL observed in the electron systems in a-IGZO TFTs.Extensive use of integrated circuits with low power consumption [1] is required in the fabrication of modern electronic devices. Among these consumer products, thin-film-transistor (TFT) nonvolatile memory devices based on oxide semiconductors have recently attracted great attention owing to their potential application in flexible system-on-panel displays [2][3][4][5]. Amorphous InGaZnO 4 (a-IGZO) TFTs, in particular, have several advantages over other transparent conducting oxides, such as high field-effect mobilities [6][7][8][9][10][11], small subthreshold swings with low off-state currents [12], good uniformity, and tunable carrier concentrations even when deposited at room temperature [13,14]. Therefore, they are a promising alternative to amorphous silicon TFTs as switching and driving devices for application in activematrix liquid-crystal displays and organic light-emitting diode displays.Apart from the investigation of a few quality issues of a-IGZO TFTs for practical applications conducted so far [15][16][17], research on their fundamental electrical properties at low temperatures is necessary for exploring quantum corrections to the conductivity of these carrier systems with disorders. Quantum interference and weak localization have been studied in electron systems in various materials [18][19][20][21][22][23][24][25] . InZnO semiconductor films and nanowires, in particular, have raised special interest because of their intricate physical properties and potential applications in nanoelectronic and spintronic devices [26][27][28][29][30][31][32][33]. However, few comprehensive in-depth studies of the low-temperature electrical transports in InZnO and similar multicomponent oxide semiconductors were condected. Recently, we reported an intriguing observation of controllable competition between weak localization (WL) and weak antilocalization (WAL) in the electron systems in a-IGZO TFTs under variation of the gate voltage or the temperature [34], but the underlying mechanism remains undetermined. More studies are re- * These authors contributed equally to this work. † quired to further understand the quantum interference in these systems.In this work, we extend our study of the competing WL and WAL observed in a-IGZO TFTs by examining the low-temperature channel magnetoconductivity (MC) of a series of a-IGZO TFTs with various channel dimensions. Manipulated via electric gating, the MC of all the samples r...

Weak Localization and Weak Antilocalization in Double-Gate a-InGaZnO Thin-Film Transistors

“…It is noticed that the shape of the universal curve may vary among devices with different structure fabrications. The single-gate a-IGZO TFTs in our previous experiment [12], for example, never entered the linear regime within the V G range studied, and therefore its partial universal curve of α 1 vs σ(0) did not show any changes in the slope.…”

“…Measurements on the double-gate a-IGZO TFTs with higher σ(0) (σ at zero B) allow us to investigate the evolution of the WL and WAL competitions from zero-to high-conductivity regimes. In our previous experiment on single-gate a-IGZO TFTs [12], only low-conductivity transport (σ(0) 200 × 10 −6 e 2 /h) could be studied. [23], and each of them surprisingly col-lapses onto a universal curve despite the distinct patterns of ∆σ(0.2 T) vs σ(0) obtained from different gate operations shown in Figs.…”

“…Crossovers from WL to WAL have been observed in magnetoconductivity of InZnO films via temperature variation [7,9]. However, gate-controlled quantum interference in ZnO or its doped form was not reported until very recently, when competitions between WL and WAL were discovered in singlegate a-IGZO TFTs via electric gating in our previous research [11], and an intriguing universal dependence of the respective WL and WAL contributions on the channel conductivity was observed [12]. In this paper, more information about this universal dependence is revealed by quantum magnetotransport measurements on doublegate a-IGZO TFTs with higher conductivity.…”

“…Therefore, we add a small coefficient A to the original equation [18,19] to address this issue. The magnitudes of σ of the double-gate a-IGZO TFTs are found to be ∼3 times larger than those of the single-gate a-IGZO TFTs from our previous measurements [11,12], so A is set to 3 × 10 −4 in this work to roughly compensate the difference in sample quality [22]. Eq.…”

“…Measurements on the double-gate a-IGZO TFTs with higher σ(0) (σ at zero B) allow us to investigate the evolution of the WL and WAL competitions from zero-to high-conductivity regimes. In our previous experiment on single-gate a-IGZO TFTs [12], only low-conductivity transport (σ(0) 200 × 10 −6 e 2 /h) could be studied. Figs.…”