Amorphous Oxide TFT for Normally Off Light-Emitting Devices
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Solution Overview
Problem
Conventional oxide-semiconductor thin films, such as those using ZnO, face challenges in achieving sufficient characteristics for field-effect transistors (TFTs) due to high electron mobility, oxygen defects, and difficulty in realizing a normally off state, which limits their application in flat panel displays.
Innovation Solution
The use of amorphous oxide semiconductors with specific compositions like InGaZnO, controlled to have an electronic carrier concentration of less than 1×10^18/cm^3, which are formed using techniques like pulsed laser vapor deposition and sputtering, enabling the creation of TFTs with improved ON/OFF ratios and normally off operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional oxide-semiconductor thin films (e.g., ZnO) are used for TFT active layers, then low-temperature film formation is achieved, but sufficient transistor characteristics (ON/OFF ratio, normally off state) cannot be obtained due to high electron mobility and oxygen defects
Solution Approach 1:
The invention changes the material parameters by using amorphous oxide semiconductors with specifically controlled low electronic carrier concentrations (less than 1×10^18/cm³). This parameter change resolves the contradiction by enabling both low-temperature formation and sufficient transistor characteristics through reduced carrier concentration, which lowers electron mobility to appropriate levels while maintaining the normally off state capability
Solution Approach 2:
The invention employs composite material design by combining amorphous oxide semiconductor materials (such as In-Ga-Zn-O, In-Sn-O, or In-Zn-O systems) with specific compositional ratios. This composite approach allows optimization of both formation temperature and electrical characteristics, achieving the desired balance between manufacturability and device performance
2Reliability
If amorphous oxide semiconductors with very low electronic carrier concentration are used, then normally off state is achieved, but electron mobility decreases
Solution Approach 1:
The invention optimizes the electronic carrier concentration parameter to a specific range (less than 1×10^18/cm³) rather than minimizing it completely. This controlled parameter change enables the material to achieve the normally off state while maintaining sufficient electron mobility for practical transistor operation, resolving the contradiction between these two requirements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These amorphous oxide TFTs demonstrate enhanced electron mobility, reduced electric conductivity, and the ability to achieve a normally off state, making them suitable for use in light-emitting devices and flat panel displays.
Implementation Method 1
formed using techniques like pulsed laser vapor deposition and sputtering
Implementation Method 2
formed using techniques like pulsed laser vapor deposition and sputtering
Data Source
AI summary
An object of the present invention is to provide a new light-emitting device with the use of an amorphous oxide. The light-emitting device has a light-emitting layer existing between first and second electrodes and a field effect transistor, of which the active layer is an amorphous.