Modeling and Mechanism of Enhanced Performance of In-Ga-Zn-O Thin-Film Transistors with Nanometer Thicknesses under Temperature Stress

Abstract

In-Ga-Zn-O (IGZO) nanometer thin-film transistors (TFTs) are promising candidates for liquid crystal display (LCD) drivers and human body sensors. It is critically important to study the temperature dependence of IGZO TFTs on electrical properties. However, the mechanism of the enhanced IGZO TFT function at different temperatures has not been fully determined. Here, a single transistor was used to act as a temperature sensor to save the space, and transfer curves shifting positively were found for the first time, different from conventional temperature-dependent behaviors. This behavior suggests at least two mechanisms that dominate and are responsible for the different shifts. According to the Arrhenius law, the formula between temperature (T) and threshold voltage (V TH ) was modified. Besides, two different values of activation energy (E a ) on different temperature ranges indicate that there are two main mechanisms. For further verification, different experimental approaches were conducted to study the temperature effects, including subgap density of states (DOS), X-ray photoelectron spectroscopy (XPS), and simulation experiments. This mechanism, shown here for the first time, might better the understanding of TFTs and, thus, further their applications in medicine and beyond.

Numerical Analysis of Oxygen-Related Defects in Amorphous In-W-O Nanosheet Thin-Film Transistor

“…The occupation probability f (E) describes that traps are either filled with electrons or empty; then, it has a value in the range of 0 to 1, and consequently the Fermi energy position can be determined when f (E) = 0.5. The occupation probability f (E) and thermal velocity υ n and υ p for the electron and hole in Equations ( 9) and ( 10) can be determined by assuming the Richardson coefficients (A n , A p ) of 41 A•cm −2 •k −2 [29], capture cross sections σ E and σ H of 1 × 10 12 cm 2 [30], and conduction/valance band effective density of states (N C = N V ) of 2.0 × 10 18 cm −3 , initially estimated from the carrier concentration of Hall measurements.…”

Analysis of Nitrogen-Doping Effect on Sub-Gap Density of States in a-IGZO TFTs by TCAD Simulation

“…Although a-IGZO TFT technology has made remarkable progress since it was first proposed by Nomura et al in 2004, these devices still cannot achieve the desired performance and reliability due to high-density sub-gap states existing in the bandgap of a-IGZO [4,5]. It has been demonstrated that the sub-gap defects mainly originate from oxygen-vacancyrelated (V o -related) defects induced by the structural disorder in a-IGZO [5][6][7], which degrades the electrical properties and reliability of TFTs by trapping electrons or holes in the channel layer and interfacial region under bias, light, and thermal stress [8][9][10][11]. To enhance the device performance and reliability, an in-situ nitrogen-doping (N-doping) approach during the a-IGZO active layer deposition has been proposed to suppress V o defect generation [12][13][14].…”