溶胶凝胶法制备以Al_2O_3为界面修饰层的铪铟锌氧薄膜晶体管

利用溶液法制备了以HfSiOx为绝缘层、HfInZnO为有源层、Al_2O_3为界面修饰层的TFT器件。HfSiOx薄膜经Al_2O_3薄膜修饰后,薄膜表面粗糙度从0.24nm降低至0.16nm。Al2O3薄膜与HfSiOx薄膜之间的界面接触良好,以Al_2O_3为界面修饰层的TFT器件整体性能得到提升,具体表现为:栅极电压正向和反向扫描过程中产生的阈值电压漂移显著减小,器件的阈值电压和亚阈值摆幅降低,迁移率与开关比增大。研究证明,溶液法制备Al_2O_3薄膜适合作为改善器件性能的界面修饰层。     

Comparison between N2 and O2 anneals on the integrity of an Al2O3/SiaN4/SiO2/Si memory gate stack

In this paper the endurance characteristics and trap generation are investigated to study the effects of different postdeposition anneals （PDAs） on the integrity of an Al2O3/Si3N4/SiOz/Si memory gate stack. The flat-band voltage （Vfb） turnarounds are observed in both the programmed and erased states of the N2-PDA device. In contrast, this turnaround is observed only in the erased state of the O2-PDA device. The Vfb in the programmed state of the O2-PDA device keeps increasing with increasing program/erase （P/E） cycles. Through the analyses of endurance characteristics and the low voltage round-trip current transients, it is concluded that in both kinds of device there are an unknown type of pre-existing characteristic deep traps and P/E stress-induced positive oxide charges. In the O2-PDA device two extra types of trap are also found： the pre-existing border traps and the P/E stress-induced negative traps. Based on these four types of defects we can explain the endurance characteristics of two kinds of device. The switching property of pre-existing characteristic deep traps is also discussed.     

Study on a novel vertical enhancement-mode Ga2O3 MOSFET with FINFET structure

A novel enhanced mode(E-mode)Ga₂O₃ metal-oxide-semiconductor field-effect transistor(MOSFET)with vertical FINFET structure is proposed and the characteristics of that device are numerically investigated.It is found that the concentration of the source region and the width coupled with the height of the channel mainly effect the on-state characteristics.The metal material of the gate,the oxide material,the oxide thickness,and the epitaxial layer concentration strongly affect the threshold voltage and the output currents.Enabling an E-mode MOSFET device requires a large work function gate metal and an oxide with large dielectric constant.When the output current density of the device increases,the source concentration,the thickness of the epitaxial layer,and the total width of the device need to be expanded.The threshold voltage decreases with the increase of the width of the channel area under the same gate voltage.It is indicated that a set of optimal parameters of a practical vertical enhancement-mode Ga₂O₃ MOSFET requires the epitaxial layer concentration,the channel height of the device,the thickness of the source region,and the oxide thickness of the device should be less than 5×10¹⁶ cm^-3,less than 1.5μm,between 0.1μm-0.3μm and less than 0.08μm,respectively.     

Assessment of the illumination dependency of Al2O3 and SiO2 rear‐passivated p‐type silicon solar cells

This Letter discusses an important difference between positively charged SiO₂ and negatively charged Al₂O₃ rear‐passivated p‐type Si solar cells: their illumination level dependency. For positively charged SiO₂ rear‐passivated p‐type Si solar cells, a loss in short circuit current (J_SC) and open circuit voltage (V_OC) as a function of illumination level is mainly caused by parasitic shunting and a decrease in surface recombination, respectively. Hence, the relative loss in cell conversion efficiency, J_SC, and V_OC as a function of the illumination level for SiO₂ compared to Al₂O₃ rear‐passivated p‐type Si solar cells has been measured and discussed. Subsequently, an exponential decay fit of the loss in cell efficiency is applied in order to estimate the difference in the energy output for both cell types in three different territories: Belgium (EU), Seattle and Austin (US). The observed trends in the difference in energy output between both cells, as a function of time of the year and region, are as expected and discussed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of thermal annealing sequence on the crystal phase of HfO2 and charge trap property of Al2O3/HfO2/SiO2 stacks

In this study, we investigated the effect of a post annealing sequence on the HfO₂ crystal phase and the memory window of charge trap devices with TiN-Al₂O₃-HfO₂-SiO₂-Si stacks. The charge trap dielectrics of HfO₂ were deposited by atomic layer deposition and were annealed in an oxygen environment with or without Al₂O₃ blocking oxides. X-ray diffraction analysis showed that, after thermal annealing, the predominant crystal phase of HfO₂ is divided into tetragonal and monoclinic phase depending on the presence or absence of Al₂O₃ blocking oxide. In addition, deconvolution of X-ray diffraction spectra showed that, with increasing annealing temperature, the fraction of the tetragonal phase in the HfO₂ film was enhanced with the Al₂O₃ blocking oxide, while it was reduced without the Al₂O₃ blocking oxide. Finally, measurements of program/erase and increase-step-pulse programming showed that the charge trap efficiency and the memory window of the charge trap devices increased with decreasing fraction of tetragonal HfO₂.     

An XPS Study of the Effect of La2O3 Dopant on the Dispersion and Thermal Stability of Pt/Al2O3 Catalysts

The Pt(4d)/Al(2s) XPS intensity ratio for Pt/Al₂O₃ catalysts increases with the addition of La₂O₃ as a dopant. The Pt(311) line in the X-ray diffraction pattern also broadens with the addition of La₂O₃. These data imply that doping the Pt/Al₂O₃ catalyst with La₂O₃ increases the dispersion of the platinum which in turn would be expected to increase the activity and thermal stability of the catalyst.