Investigation on energy bandgap states of amorphous SiZnSnO thin films

Analyzing Acceptor-like State Distribution of Solution-Processed Indium-Zinc-Oxide Semiconductor Depending on the In Concentration

Understanding the density of state (DOS) distribution in solution-processed indium-zinc-oxide (IZO) thin-film transistors (TFTs) is crucial for addressing electrical instability. This paper presents quantitative calculations of the acceptor-like state distribution of solution-processed IZO TFTs using thermal energy analysis. To extract the acceptor-like state distribution, the electrical characteristics of IZO TFTs with various In molarity ratios were analyzed with respect to temperature. An Arrhenius plot was used to determine electrical parameters such as the activation energy, flat band energy, and flat band voltage. Two calculation methods, the simplified charge approximation and the Meyer-Neldel (MN) rule-based carrier-surface potential field-effect analysis, were proposed to estimate the acceptor-like state distribution. The simplified charge approximation established the modeling of acceptor-like states using the charge-voltage relationship. The MN rule-based field-effect analysis validated the DOS distribution through the carrier-surface potential relationship. In addition, this study introduces practical and effective approaches for determining the DOS distribution of solution-processed IZO semiconductors based on the In molarity ratio. The profiles of the acceptor-like state distribution provide insights into the electrical behavior depending on the doping concentration of the solution-processed IZO semiconductors.

Probing the Efficacy of Large-Scale Nonporous IGZO for Visible-to-NIR Detection Capability: An Approach toward High-Performance Image Sensor Circuitry

The technological ability to detect a wide spectrum range of illuminated visible-to-NIR is substantially improved for an amorphous metal oxide semiconductor, indium gallium zinc oxide (IGZO), without employing an additional photoabsorber. The fundamentally tuned morphology via structural engineering results in the creation of nanopores throughout the entire thickness of ∼30 nm. See-through nanopores have edge functionalization with vacancies, which leads to a large density of substates near the conduction band minima and valence band maxima. The presence of nanoring edges with a high concentration of vacancies is investigated using chemical composition analysis. The process of creating a nonporous morphology is sophisticated and is demonstrated using a wafer-scale phototransistor array. The performance of the phototransistors is assessed in terms of photosensitivity (S) and photoresponsivity (R); both are of high magnitudes (S = 8.6 × 10⁴ at λ_ex = 638 nm and P_inc = 512 mW cm^2-; R = 120 A W^1- at P_inc = 2 mW cm^2- for the same λ_ex). Additionally, the 7 × 5 array of 35 phototransistors is effective in sensing and reproducing the input image by responding to selectively illuminated pixels.

Sublimation-doping with super bases for high-performance solution-processed heterojunction oxide thin film transistors

We elucidate how non-destructive sublimation-doping of In₂O₃/ZnO heterojunctions with various amidine-based organic dopants affects the degree of band bending of the heterojunction and thus the overall performance of solution-processed heterojunction oxide thin-film transistors (TFTs). Ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy analyses show that the stronger the basicity of the dopant, the smaller the E_C - E_F of ZnO that can be induced within a short doping time, resulting in a high electron mobility due to the increased electron density of the In₂O₃ layer at the vicinity of the heterointerface. Mott-Schottky analysis combined with secondary ion mass spectroscopy shows the preferential modification of E_C - E_F selectively for the ZnO layer. The use of a super base with the highest basicity exhibits a high electron mobility of 17.8 cm² V^-1 s^-1 for the SiO₂ and 37.8 cm² V^-1 s^-1 on average (46.6 cm² V^-1 s^-1 maximum) for the ZrO₂ dielectric layers and enhanced operational bias-stress stability via sublimation-doping for 6 min, which can be attributed to the trap-filled, percolation-limited charge transport behavior. Reproducibility tests are conducted for more than 50 independently fabricated TFTs using the optimized doping technique, and electron mobility distributions with deviations <±10% are demonstrated. This study shows that sublimation doping with super bases can be a good solution for high mobility oxide TFTs with stability and reliability.

Characteristics and Electronic Band Alignment of a Transparent p-CuI/n-SiZnSnO Heterojunction Diode with a High Rectification Ratio

Transparent p-CuI/n-SiZnSnO (SZTO) heterojunction diodes are successfully fabricated by thermal evaporation of a (111) oriented p-CuI polycrystalline film on top of an amorphous n-SZTO film grown by the RF magnetron sputtering method. A nitrogen annealing process reduces ionized impurity scattering dominantly incurred by Cu vacancy and structural defects at the grain boundaries in the CuI film to result in improved diode performance; the current rectification ratio estimated at ±2 V is enhanced from ≈10⁶ to ≈10⁷. Various diode parameters, including ideality factor, reverse saturation current, offset current, series resistance, and parallel resistance, are estimated based on the Shockley diode equation. An energy band diagram exhibiting the type-II band alignment is proposed to explain the diode characteristics. The present p-CuI/n-SZTO diode can be a promising building block for constructing useful optoelectronic components such as a light-emitting diode and a UV photodetector.