IGZO Photodiode Oxygen Gradient for UV-Visible Signal Discrimination
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Solution Overview
Problem
Conventional light sensors using amorphous silicon photodiodes struggle to distinguish between ultraviolet and visible light signals, limiting their applications due to the introduction of photoelectric effects from both types of light.
Innovation Solution
A photodiode structure comprising a N-type amorphous indium gallium zinc oxide (IGZO) layer with varying oxygen content, optionally including a P-type semiconductor layer, is used in conjunction with a thin-film transistor, where the oxygen content in the intrinsic amorphous IGZO layer is greater than in the N-type layer, and the photodiode is fabricated using a sputtering process with controlled oxygen to argon flow ratios to enhance selectivity for ultraviolet light absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional amorphous silicon photodiodes are used, then photoelectric conversion is achieved, but both ultraviolet and visible light signals cannot be distinguished
Solution Approach 1:
The patent applies local quality by creating distinct regions within the photodiode structure with different oxygen contents. The intrinsic layer has higher oxygen content (20-40 at%) while the N-type layer has lower oxygen content (5-20 at%), making each layer respond selectively to different light wavelengths. This spatial variation in material composition enables the device to distinguish between UV and visible light signals.
Solution Approach 2:
The patent utilizes parameter changes by varying the oxygen content parameter in the IGZO layers to achieve different photoelectric responses. By controlling oxygen concentration during sputtering deposition, the band structure and optical absorption characteristics are modified, allowing selective detection of UV light in the intrinsic layer versus visible light in the N-type layer.
2Reliability
If amorphous silicon is doped to form PIN photodiode, then photoelectric conversion is enabled, but selectivity for ultraviolet light is reduced
Solution Approach 1:
The patent employs composite materials by combining IGZO layers with different oxygen stoichiometries within a single photodiode structure. The composite nature of having both oxygen-rich intrinsic layer and oxygen-deficient N-type layer creates complementary photoelectric properties that maintain high conversion efficiency while adding UV selectivity through the intrinsic layer's broader UV absorption spectrum.
3Measurement precision
If oxygen content in intrinsic amorphous IGZO is increased, then ultraviolet light absorption is enhanced, but charge carrier mobility may be affected
Solution Approach 1:
The patent applies segmentation by dividing the photodiode into functionally distinct layers: an intrinsic layer optimized for UV absorption with high oxygen content, and an N-type layer optimized for charge carrier transport with lower oxygen content. This segmentation allows each layer to be independently optimized for its specific function without compromising the other, as the N-type layer's higher mobility compensates for any mobility reduction in the intrinsic layer.
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
The solution allows for effective separation of ultraviolet and visible light signals, enabling broader applications in UV light sensors, switches, and solar panels by enhancing charge carrier mobility and selectively absorbing UV light while transmitting visible light.
Implementation Method 1
Since amorphous silicon has photoelectric characteristics, amorphous silicon has been utilized in light sensor devices... both ultraviolet and visible light may introduce photoelectric effects in the conventional photodiode
Implementation Method 2
a sputtering process under an atmosphere containing oxygen and argon is performed to continuously form the N-type semiconductor layer and the intrinsic semiconductor layer
Data Source
AI summary
A photodiode, a light sensor and a fabricating method thereof are disclosed. An n-type semiconductor layer and an intrinsic semiconductor layer of the photodiode respectively comprise n-type amorphous indium gallium zinc oxide (IGZO) and intrinsic IGZO. The oxygen content of the intrinsic amorphous IGZO is greater than the oxygen content of the n-type amorphous IGZO. A light sensor comprise the photodiode is also disclosed.