Electrical instability of amorphous indium-gallium-zinc oxide thin film transistors under monochromatic light illumination

Abstract

The electrical instability behaviors of a positive-gate-bias-stressed amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistor (TFT) are studied under monochromatic light illumination. It is found that as the wavelength of incident light reduces from 750 nm to 450 nm, the threshold voltage of the illuminated TFT shows a continuous negative shift, which is caused by photo-excitation of trapped electrons at the channel/dielectric interface. Meanwhile, an increase of the sub-threshold swing (SS) is observed when the illumination wavelength is below 625 nm ($2.0 eV). The SS degradation is accompanied by a simultaneous increase of the field effect mobility (l FE) of the TFT, which then decreases at even shorter wavelength beyond 540 nm ($2.3 eV). The variation of SS and l FE is explained by a physical model based on generation of singly ionized oxygen vacancies (V o þ) and double ionized oxygen vacancies (V o 2þ) within the a-IGZO active layer by high energy photons, which would form trap states near the mid-gap and the conduction band edge, respectively.

Oxide Semiconductor Phototransistor with Organolead Trihalide Perovskite Light Absorber

“…For IGZO TFT under the cyclically switched illumination, the value of I D is so small that it has to be multiplied by 2 × 10 3 in order to be clearly observed in the presented figure (λ = 550 nm). Even worse, when operated under continuous illumination for a long period (300 s), the IGZO TFT became highly unstable by showing a continuously increased conductance (Figure a), which is related to sub‐bandgap excitation of oxygen vacancy defects . This unstable behavior under continuous pulse illumination has the same physical origin as the well‐known persist photoconductivity (PPC) phenomenon, where oxide photosensors when illuminated would maintain high photocurrent for a long period even after the light is turned off.…”

The Influence of Annealing Temperature on Amorphous Indium‐Zinc‐Tungsten Oxide Thin‐Film Transistors

“…The calculated µ FE value rises from 3.0 to 7.3, 9.3, and 16.2 cm 2 V −1 s −1 as the temperature rises from 150 to 200, 250, and 300 °C. It is believed that in the channel layer there are three forms of oxygen vacancies: non‐ionized V O 0 vacancies acting as deep localized states near the valence‐band maximum (VBM), singly ionized V O + vacancies, and doubly ionized V O 2+ vacancies acting as shallow donors near the conduction band minimum (CBM) . In addition, most of the oxygen vacancies act as the deep localized state.…”

Plasma-Assisted Atomic Layer Deposition of High-Density Ni Nanoparticles for Amorphous In-Ga-Zn-O Thin Film Transistor Memory

“…Meanwhile, the resulting transfer curves also show a deterioration trend in the sub-threshold swing (SS); this can be understood as follows. When a negative bias is applied to the gate, some neutral oxygen vacancies in the IGZO channel layer can be ionized, and these positively charged oxygen vacancies are accumulated at the IGZO/Al 2 O 3 interface, resulting in the SS degradation [ 31 ]. Compared with the high programming efficiency of the current memory devices, the relatively low erasing efficiency can be explained as follows.…”