Layered Semiconductor Design for Enhanced Spectral Sensitivity
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Summary
Problems
Existing environmental light sensors have inadequate spectral sensitivity, often being too sensitive to long wavelengths (red) and not sensitive enough to short wavelengths (blue), leading to variations in component characteristics that limit their value.
Innovation solutions
A layered semiconductor design with a highly doped substrate and a more lightly doped layer, where the lightly doped layer and base layer have regions of different thicknesses, allowing for improved sensitivity to blue light and reduced sensitivity to red light, enabling the production of more reproducible semiconductor components.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If the thickness of the lightly doped layer is set to a comparatively small value (2.5 μm to 3 μm) to improve spectral sensitivity adaptation, then the sensitivity to long wavelengths (red light) is reduced, but the thickness of the anode/base layer must also be set relatively thin (approximately 1 μm) which leads to huge variations in transistor characteristic values
Why choose this principle:
The patent divides the lightly doped layer into two distinct regions: a first region with a first thickness (e.g., 2.5-3 μm) for the photodiode function, and a second region with a second thickness (e.g., 5-15 μm) for the transistor function. This segmentation allows each region to be optimized independently – the thinner first region adapts spectral sensitivity by reducing red light sensitivity, while the thicker second region provides sufficient vertical dimension for reproducible transistor characteristics.
Principle concept:
If the thickness of the lightly doped layer is set to a comparatively small value (2.5 μm to 3 μm) to improve spectral sensitivity adaptation, then the sensitivity to long wavelengths (red light) is reduced, but the thickness of the anode/base layer must also be set relatively thin (approximately 1 μm) which leads to huge variations in transistor characteristic values
Why choose this principle:
Different regions of the lightly doped layer are assigned different thicknesses to fulfill different functional requirements. The first region (thinner) is optimized for photodiode operation and spectral adaptation, while the second region (thicker) is optimized for transistor operation and characteristic consistency. This local differentiation resolves the contradiction between spectral adaptation and transistor reliability.
Application Domain
Data Source
AI summary:
A layered semiconductor design with a highly doped substrate and a more lightly doped layer, where the lightly doped layer and base layer have regions of different thicknesses, allowing for improved sensitivity to blue light and reduced sensitivity to red light, enabling the production of more reproducible semiconductor components.
Abstract
A photosensitive transistor is disclosed herein that includes: a semiconductor substrate of the first conductivity type as a collector layer; above it a less doped layer of the first conductivity type having regions of different thickness; a semiconductor base layer of the second conductivity type above at least parts of the regions of the less doped layer; and an emitter layer of the first conductivity type above at least parts of the base layer, but not above at least one part of the part of the base layer disposed above the thinner region of the less doped layer.