N-channel TFT Doping Structure for OLED Display Uniformity
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Solution Overview
Problem
The reliability and lifetime of OLED display circuits are compromised due to the hot-carrier effect in N-channel TFTs, which affects image uniformity and display performance.
Innovation Solution
The N-channel TFT structure includes a substrate with an active layer featuring a highly-doped source region and a lightly-doped drain region, where at least part of each is located under the gate region, reducing threshold voltage variation and hot-carrier effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If N-channel TFT is used to replace P-channel TFT, then image uniformity is improved, but reliability is worsened due to hot-carrier effect
Solution Approach 1:
The patent applies different doping concentrations to different regions of the active layer: a first doped region with first doping concentration and a second doped region with second doping concentration higher than the first. This local quality differentiation reduces hot-carrier effects in specific areas while maintaining the benefits of N-channel TFT for image uniformity.
Solution Approach 2:
The patent changes the doping concentration parameter across different regions of the active layer. By having a higher doping concentration in the second doped region compared to the first doped region, the patent optimizes the balance between image uniformity and reliability by controlling carrier distribution and reducing hot-carrier effects.
2Device complexity
If P-channel TFT is used for driving OLED, then circuit simplicity is maintained, but image uniformity is poor due to threshold voltage variation
Solution Approach 1:
The patent uses N-channel TFT with spatially varying doping concentrations in the active layer. This local quality approach addresses the threshold voltage variation problem by creating regions with different electrical properties, thereby improving image uniformity while maintaining circuit simplicity.
Solution Approach 2:
The patent changes the doping concentration parameter across the active layer regions. The second doped region has a higher doping concentration than the first doped region, which modifies the threshold voltage distribution and improves image uniformity without complicating the circuit structure.
Data Source
AI summary
An N-channel TFT and OLED display apparatus and electronic device using the same are disclosed. The N-channel TFT comprises a a substrate; an active layer on the substrate, wherein the active layer comprises an N type source region and an N type drain region; a gate dielectric layer on the active layer; and a gate region on the gate dielectric layer. At least a part of the highly-doped source region is located under the gate region, and at least a part of the lightly-doped drain region is located under the gate region.