Extraction of Subgap Density of States in Amorphous InGaZnO Thin-Film Transistors by Using Multifrequency Capacitance–Voltage Characteristics

Abstract

An extraction technique for subgap density of states (DOS) in an n-channel amorphous InGaZnO thin-film transistor (TFT) by using multifrequency capacitance-voltage (C-V ) characteristics is proposed and verified by comparing the measured I-V characteristics with the technology computeraided design simulation results incorporating the extracted DOS as parameters. It takes on the superposition of exponential tail states and exponential deep states with characteristic parameters for N TA = 1.1×10 17 cm −3 ·eV −1 , N DA = 4×10 15 cm −3 ·eV −1 , kT TA = 0.09 eV, and kT DA = 0.4 eV. The proposed technique allows obtaining the frequency-independent C-V curve, which is very useful for oxide semiconductor TFT modeling and characterization, and considers the nonlinear relation between the energy level of DOS and the gate voltage V GS . In addition, it is a simple, fast, and accurate extraction method for DOS in amorphous InGaZnO TFTs without optical illumination, temperature dependence, and numerical iteration.Index Terms-Amorphous, density of states (DOS), indiumgallium-zinc-oxide (InGaZnO), multifrequency capacitancevoltage (C-V ) characteristics, technology computer-aided design (TCAD), thin-film transistors (TFTs).

Effect of direct current sputtering power on the behavior of amorphous indium-gallium-zinc-oxide thin-film transistors under negative bias illumination stress: A combination of experimental analyses and device simulation

“…Quantitative analyses are carried out by the combination of extracted sub-gap density of states (DOS) and device simulation. [12][13][14][15] Studies indicate that peroxide formation reflects well the observed behavior of the TFT under NBIS.…”

“…In detail, the density distribution of acceptor-like sub-gap states, g A (E), and that of donor-like sub-gap states, g D (E), were extracted by using the frequency-dependence 13 and photonic response 14 of the C-V characteristics, respectively. The current-voltage (I-V) characteristics were calculated by combining the extracted DOS and a sub-gap DOS-based device simulator (DeAOTS).…”

Origin of instability by positive bias stress in amorphous Si-In-Zn-O thin film transistor

“…It was reported that the acceptor-like DOS extracted from MFM technique was originated from the channel/GI interface trap and the bulk trap in the channel layer. 9 Therefore, in terms of the DOSs in SIZO-TFTs, the decrease in l FE and the further positive V th shift of 3SIZO-TFT than those of 1SIZO-TFT can be explained by the increase of total trap density, which is within energy range from E c to 0.3 eV below E c , rather than the decrease of oxygen vacancies. It was reported that 1 wt.…”

“…9 Mo, as a gate electrode, was deposited on glass substrate by direct current sputtering method, and then amorphous SIZO active layer was grown by the radio frequency magnetron sputtering method at room temperature on 200 nm thick SiN x as gate insulator (GI). More details of device fabrication were described in our previous work.…”

Analytical surface-potential-based drain current model for amorphous InGaZnO thin film transistors

“…Whereas the electrical properties of a-IGZO TFTs were extensively investigated by several research groups, [1][2][3][4][5][6][7] and the trap distributions were extracted and analyzed in recent published work, [8][9][10][11] there have been few reports on drain current modeling. Recently, published papers have proposed technology computer-aided design (TCAD) device simulators to reproduce the measured current-voltage characteristics and to extract the subgap density of states.…”