Keisuke Ide

Effects of excess oxygen on operation characteristics of amorphous In-Ga-Zn-O thin-film transistors

Operation characteristics of amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) were improved to a subthreshold voltage swing (S) of 217 mV (decade)−1, a mobility of ∼11.4 cm2 (Vs)−1, and a threshold voltage (Vth) of 0.1 V by O3 annealing at a temperature as low as 150 °C. However, the O3 annealing at 300 °C caused serious deterioration and exhibited a bistable transition between a large S state and a large Vth state. This transition is attributed to incorporation of excess oxygen and associated subgap defects with a negative-U characteristic. It also explains why a-IGZO channels deposited at high oxygen pressures do not produce operating TFTs.

Structural relaxation in amorphous oxide semiconductor, a-In-Ga-Zn-O

Amorphous In-Ga-Zn-O (a-IGZO) is expected as a backplane transistor material to drive next-generation flat-panel and flexible displays. It has been elucidated that thermal annealing even at low temperatures <200 °C reduces deep subgap defects and those at ≥300 °C further improve device characteristics, stability, and uniformity. These temperatures are much lower than the reported crystallization temperature (TX ∼ 600 °C). In this work, we investigate effects of thermal annealing on the structural and optical properties of a-IGZO thin films. We performed classical molecular dynamics simulation (CMD) and optical interference analyses including spectroscopic ellipsometry (SE). CMD reproduced the x-ray diffraction pattern of a-IGZO and exhibited a glass transition. Experimentally, it was found that TX depends largely on deposition methods and conditions, probably due to different chemical compositions. Sputter-deposited a-IGZO films exhibited onset TX ∼ 600 °C and crystalline volume fraction XC increased line...

Effects of residual hydrogen in sputtering atmosphere on structures and properties of amorphous In-Ga-Zn-O thin films

We investigated the effects of residual hydrogen in sputtering atmosphere on subgap states and carrier transport in amorphous In-Ga-Zn-O (a-IGZO) using two sputtering systems with different base pressures of ∼10−4 and 10−7 Pa (standard (STD) and ultrahigh vacuum (UHV) sputtering, respectively), which produce a-IGZO films with impurity hydrogen contents at the orders of 1020 and 1019 cm−3, respectively. Several subgap states were observed by hard X-ray photoemission spectroscopy, i.e., peak-shape near-valence band maximum (near-VBM) states, shoulder-shape near-VBM states, peak-shape near-conduction band minimum (near-CBM) states, and step-wise near-CBM states. It was confirmed that the formation of these subgap states were affected strongly by the residual hydrogen (possibly H2O). The step-wise near-CBM states were observed only in the STD films deposited without O2 gas flow and attributed to metallic In. Such step-wise near-CBM state was not detected in the other films including the UHV films even deposit...

Solid phase epitaxial growth of high mobility La:BaSnO3 thin films co-doped with interstitial hydrogen

This work presents the solid phase epitaxial growth of high mobility La:BaSnO3 thin films on SrTiO3 single crystal substrates by crystallization through thermal annealing of nanocrystalline thin films prepared by pulsed laser deposition at room temperature. The La:BaSnO3 thin films show high epitaxial quality and Hall mobilities up to 26 ± 1 cm2/Vs. Secondary ion mass spectroscopy is used to determine the La concentration profile in the La:BaSnO3 thin films, and a 9%–16% La doping activation efficiency is obtained. An investigation of H doping to BaSnO3 thin films is presented employing H plasma treatment at room temperature. Carrier concentrations in previously insulating BaSnO3 thin films were increased to 3 × 1019 cm−3 and in La:BaSnO3 thin films from 6 × 1019 cm−3 to 1.5 × 1020 cm−3, supporting a theoretical prediction that interstitial H serves as an excellent n-type dopant. An analysis of the free electron absorption by infrared spectroscopy yields a small (H,La):BaSnO3 electron effective mass of 0....

Electron effective mass and mobility limits in degenerate perovskite stannateBaSnO3

The high room temperature mobility and the electron effective mass in BaSnO

Room-temperature fabrication of light-emitting thin films based on amorphous oxide semiconductor

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Light Irradiation History Sensor Using Amorphous In-Ga-Zn-O Thin-Film Transistor Exposed to Ozone Annealing

are investigated in depth by evaluation of the free carrier absorption observed in infrared spectra for epitaxial films with free electron concentrations from

Effects of working pressure and annealing on bulk density and nanopore structures in amorphous In–Ga–Zn–O thin-film transistors

8.3 \times 10^{18}

SnS thin films prepared by H2S-free process and its p-type thin film transistor

to

Why high-pressure sputtering must be avoided to deposit a-In-Ga-Zn-O films

7.3 \times 10^{20}