Amorphous Oxide Field-Effect Transistor for Flexible Substrates
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Solution Overview
Problem
Conventional field-effect transistors employing silicon thin films cannot be directly formed on less heat-resistant resin substrates due to high-temperature requirements, and oxide semiconductor transistors struggle to simultaneously achieve transparency, excellent electric properties, effective current leakage prevention, and good adhesiveness between the active layer and substrate.
Innovation Solution
A field-effect transistor with an amorphous oxide active layer having an electron carrier concentration lower than 10^18/cm^3, which is transparent and features a lamination structure or a passivation layer to enhance adhesiveness and prevent current leakage, using oxides containing In, Zn, and Sn, and a gate-insulating film with a layered structure for improved interfacial properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If oxide semiconductor thin film is used as active layer, then film formation temperature is reduced, but transparency and electric properties cannot be simultaneously satisfied
Solution Approach 1:
The patent changes the material composition parameters of the oxide semiconductor from conventional ZnO to In-Ga-Zn-O system with specific atomic ratios (0.2≤x≤1.0, 0.05≤y≤0.5), which enables simultaneous achievement of low-temperature formation, high transparency, and excellent electric properties with electron mobility exceeding 10 cm²/Vs
Solution Approach 2:
The patent employs composite oxide semiconductor material InxGa1-xO3(ZnO)m combining multiple metal oxides, where In2O3 provides high carrier concentration, Ga2O3 enhances stability and reduces oxygen defects, and ZnO contributes to amorphous structure formation, achieving synergistic effects for superior transistor performance
2Illumination intensity
If transparent electrode is used, then transparency is improved, but electrical conductivity decreases
Solution Approach 1:
The In-Ga-Zn-O oxide semiconductor layer serves multiple functions simultaneously: it acts as the active layer providing semiconductor functionality, as a transparent electrode providing electrical conductivity, and maintains high transparency. This multi-functional material eliminates the need for separate transparent electrode layers while achieving both high transparency and excellent electrical conductivity
Solution Approach 2:
By adjusting the composition parameters (x and y ratios) and controlling the film formation conditions, the patent optimizes the balance between transparency and electrical conductivity, achieving electron mobility of 10 cm²/Vs or more while maintaining high visible light transparency
3Illumination intensity
If amorphous oxide with low electron carrier concentration is used, then transparency is improved, but current leakage increases
Solution Approach 1:
The patent precisely controls the electron carrier concentration parameter within the range of 1×10^16 to 1×10^18 cm^-3 by adjusting composition ratios and film formation conditions, achieving the optimal balance between transparency and current leakage prevention, with off-state current density of 1×10^-15 A or less
Solution Approach 2:
The patent creates different functional regions within the oxide semiconductor layer by controlling local composition variations, where the bulk maintains low carrier concentration for transparency while the interface regions with gate insulator and source/drain electrodes develop appropriate carrier concentrations for effective current control and leakage prevention
Data Source
AI summary
A novel field-effect transistor is provided which employs an amorphous oxide. In an embodiment of the present invention, the transistor comprises an amorphous oxide layer containing electron carrier at a concentration less than 1×10−18/cm3, and the gate-insulating layer is comprised of a first layer being in contact with the amorphous oxide and a second layer different from the first layer.