Oxide Semiconductor Transistor Gate Voltage Recovery
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Solution Overview
Problem
Transistors using oxide semiconductors exhibit unstable electrical characteristics, particularly when negative bias is applied with light of wavelength 400 nm or less, leading to deterioration in threshold voltage and image display performance.
Innovation Solution
Applying a voltage of 20 V or higher to the gate of the transistor for 1 millisecond or longer during specific selection periods in frame periods helps recover the transistor characteristics to their pre-deterioration state by controlling the scan and signal lines in a display device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If negative bias is applied to the gate while irradiating with light of wavelength 400 nm or less, then the transistor can be driven, but threshold voltage shifts and characteristics deteriorate
Solution Approach 1:
The patent applies a positive voltage to the gate before or during the period when negative bias and light irradiation occur, creating a counteracting effect that prevents threshold voltage shift. This preliminary protective action counterbalances the harmful combination of negative bias and light exposure, maintaining transistor characteristics stable during operation.
2Speed
If oxide semiconductor is used as semiconductor layer, then high electron mobility can be achieved, but electrical characteristics become unstable under certain conditions
Solution Approach 1:
The patent changes the voltage parameter applied to the gate, specifically applying a positive voltage of a predetermined level during periods when the transistor is subjected to light irradiation. This parameter change in gate voltage compensates for the instability inherent in oxide semiconductor transistors, allowing high electron mobility to be maintained while improving electrical characteristics stability under varying environmental conditions.
3Reliability
If high voltage is applied to the gate for extended period, then transistor characteristics can be recovered, but power consumption increases
Solution Approach 1:
The patent applies high positive voltage to the gate periodically rather than continuously, specifically during selection periods or when deterioration is detected. This periodic application of high voltage recovers transistor characteristics while minimizing overall power consumption compared to continuous high voltage application, balancing reliability recovery with energy efficiency.
Data Source
AI summary
A method for driving a display device in which characteristics of a transistor including an oxide semiconductor can approximately be recovered to characteristics before deterioration is provided. In the method for driving the display device, by which images are displayed with the use of a plurality of frame periods, the display device is driven so that a voltage of 20 V or higher can be applied to a gate of a transistor, which is a driving element, for 1 millisecond or longer in a period, in which any one of scan lines is selected, in each frame period. For a plurality of frame periods, the rows are selected so that a voltage of 20 V or higher is applied to gates of all of the transistors which are driving elements for 1 millisecond or longer, whereby characteristics of the transistor can approximately be recovered to characteristics before deterioration.