Low-Frequency Noise in Amorphous Indium Zinc Oxide Thin Film Transistors with Aluminum Oxide Gate Insulator

Low-frequency noise（LFN） in all operation regions of amorphous indium zinc oxide（a-IZO） thin film transistors（TFTs） with an aluminum oxide gate insulator is investigated. Based on the LFN measured results, we extract the distribution of localized states in the band gap and the spatial distribution of border traps in the gate dielectric,and study the dependence of measured noise on the characteristic temperature of localized states for a-IZO TFTs with Al2 O3 gate dielectric. Further study on the LFN measured results shows that the gate voltage dependent noise data closely obey the mobility fluctuation model, and the average Hooge＇s parameter is about 1.18×10^-3.Considering the relationship between the free carrier number and the field effect mobility, we simulate the LFN using the △N-△μ model, and the total trap density near the IZO/oxide interface is about 1.23×10^18 cm^-3eV^-1.

Double-layer indium doped zinc oxide for silicon thin-film solar cell prepared by ultrasonic spray pyrolysis

Indium doped zinc oxide （ZnO：In） thin films were prepared by ultrasonic spray pyrolysis on corning eagle 2000 glass substrate. 1 and 2 at.% indium doped single-layer ZnO：In thin films with different amounts of acetic acid added in the initial solution were fabricated. The 1 at.% indium doped single-layers have triangle grains. The 2 at.% indium doped single-layer with 0.18 acetic acid adding has the resistivity of 6.82 × 10^-3 Ω. cm and particle grains. The doublelayers structure is designed to fabricate the ZnO：In thin film with low resistivity （2.58 × 10^-3 Ω. cm） and good surface morphology. It is found that the surface morphology of the double-layer ZnO：In film strongly depends on the substratelayer, and the second-layer plays a large part in the resistivity of the doublewlayer ZnO：In thin film. Both total and direct transmittances of the double-layer ZnO：In film are above 80% in the visible light region. Single junction a-Si：H solar cell based on the double-layer ZnO：In as front electrode is also investigated.

High-throughput fabrication and semi-automated characterization of oxide thin film transistors

High throughput experimental methods are known to accelerate the rate of research,development,and deployment of electronic materials.For example,thin films with lateral gradients in composition,thickness,or other parameters have been used alongside spatially-resolved characterization to assess how various physical factors affect the material properties under varying measurement conditions.Similarly,multi-layer electronic devices that contain such graded thin films as one or more of their layers can also be characterized spatially in order to optimize the performance.In this work,we apply these high throughput experimental methods to thin film transistors(TFTs),demonstrating combinatorial channel layer growth,device fabrication,and semi-automated characterization using sputtered oxide TFTs as a case study.We show that both extrinsic and intrinsic types of device gradients can be generated in a TFT library,such as channel thickness and length,channel cation compositions,and oxygen atmosphere during deposition.We also present a semi-automated method to measure the 44 devices fabricated on a 50 mm×50 mm substrate that can help to identify properly functioning TFTs in the library and finish the measurement in a short time.Finally,we propose a fully automated characterization system for similar TFT libraries,which can be coupled with high throughput data analysis.These results demonstrate that high throughput methods can accelerate the investigation of TFTs and other electronic devices.

Influence of white light illumination on the performance of a-IGZO thin film transistor under positive gate-bias stress

The influence of white light illumination on the stability of an amorphous In GaZnO thin film transistor is investigated in this work. Under prolonged positive gate bias stress, the device illuminated by white light exhibits smaller positive threshold voltage shift than the device stressed under dark. There are simultaneous degradations of field-effect mobility for both stressed devices, which follows a similar trend to that of the threshold voltage shift. The reduced threshold voltage shift under illumination is explained by a competition between bias-induced interface carrier trapping effect and photon-induced carrier detrapping effect. It is further found that white light illumination could even excite and release trapped carriers originally exiting at the device interface before positive gate bias stress, so that the threshold voltage could recover to an even lower value than that in an equilibrium state. The effect of photo-excitation of oxygen vacancies within the a-IGZO film is also discussed.

Effects of annealing rate and morphology of sol–gel derived ZnO on the performance of inverted polymer solar cells

The effects of annealing rate and morphology of sol–gel derived zinc oxide （ZnO） thin films on the performance of inverted polymer solar cells （IPSCs） are investigated. ZnO films with different morphologies are prepared at different annealing rates and used as the electron transport layers in IPSCs. The undulating morphologies of ZnO films fabricated at annealing rates of 10 ℃/min and 3 ℃/min each possess a rougher surface than that of the ZnO film fabricated at a fast annealing rate of 50 ℃/min. The ZnO films are characterized by atomic force microscopy （AFM）, optical transmittance measurements, and simulation. The results indicate that the ZnO film formed at 3 ℃/min possesses a good-quality contact area with the active layer. Combined with a moderate light-scattering, the resulting device shows a 16% improvement in power conversion efficiency compared with that of the rapidly annealed ZnO film device.

Influence of substrate temperature on in situ-textured ZnO thin films grown by MOCVD

The influence of substrate temperature on microstructure, electrical and optical properties of in situ- textured zinc oxide （ZnO） films fabricated by metal organic chemical vapor deposition （MOVCD） had been investigated. Results indicated that the substrate tempera- ture played a very important role on preparation of ZnO thin film. With the raising of temperature, firstly ZnO crystals were perpendicular to the substrate, then they were grown inclining toward the substrate, finally ZnO crystals grown in layers but not regular. Consequently, ZnO film surface morphology changed from smooth to a pyramid structure and then disappeared little by little. Moreover, it was also found in this study that ZnO film was characterized with high crystallinity, low resistivity （2.17 x 10 2） and high transmittance （〉 80%）. These results suggested that ZnO thin film is suitable for front electrode of silicon thin film solar cell.