Photo Sensor Transparent Conductive Layer Dark Current Reduction
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Solution Overview
Problem
Conventional embedded-on-glass ambient light sensors have poor sensitivity due to high dark current levels, limiting their effectiveness in detecting ambient light variations and adjusting backlight brightness in mobile information products.
Innovation Solution
A photo sensor design featuring a patterned transparent conductive layer that covers the boundaries of the intrinsic and doped regions, electrically connected to a shielding conductive layer, which reduces dark current by altering the electric field and enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional embedded-on-glass photo sensor is used, then the device volume is reduced and cost is saved, but the sensitivity is poor due to high dark current
Solution Approach 1:
The transparent conductive layer is divided into multiple isolated conductive regions that are positioned over specific areas of the semiconductor layer. Each conductive region is electrically isolated from others, allowing independent control of electric fields in different regions. This segmentation enables selective modulation of the electric field to suppress dark current while maintaining photo detection capability.
Solution Approach 2:
The transparent conductive layer acts as an intermediary element between the incident light and the semiconductor layer. By introducing this intermediate layer with controlled electrical properties, the patent enables modulation of the electric field in the depletion region, which suppresses dark current generation while allowing light to pass through to generate photocurrent.
2Measurement precision
If the photo sensor is disposed close to the LCD screen, then the sensing accuracy is improved, but the dark current increases
Solution Approach 1:
The patent applies different electrical properties to different regions of the photo sensor by positioning conductive regions selectively over the semiconductor layer. The transparent conductive layer creates localized electric field enhancements in specific areas, allowing differential control of charge carrier generation and suppression in different regions. This local quality variation enables improved sensing accuracy while controlling dark current.
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 significantly improves sensitivity by reducing dark current, allowing for more accurate ambient light detection and better backlight adjustment, thereby conserving battery power and enhancing display performance.
Implementation Method 1
A patterned transparent conductive layer positioned on a dielectric layer, covering a boundary of the intrinsic region and a first doped region and a boundary of the intrinsic region and a second doped region of the patterned semiconductor layer, wherein the patterned transparent conductive layer is electrically connected to the patterned shielding conductive layer
Implementation Method 2
When light illuminates the photo sensor 10, the intrinsic region 26 will be excited to form electron-hole pairs, resulting in photocurrent that can be outputted through the contact elements 32
Data Source
AI summary
A method of fabricating a photo sensor includes the following steps. First, a substrate is provided, having a conductive layer, a buffer dielectric layer, a patterned semiconductor layer, a dielectric layer, and a planarization layer disposed thereon from bottom to top, wherein the patterned semiconductor layer comprises a first doped region, an intrinsic region, and a second doped region disposed in order. Then, the planarization layer is patterned to form an opening in the planarization layer to expose a portion of the dielectric layer, wherein the opening is positioned on the intrinsic region and portions of the first and the second doped regions. Thereafter, at least a patterned transparent conductive layer is formed in the opening, covering the boundary of the intrinsic region and the first doped region and the boundary of the intrinsic region and the second doped region.