Segmented LED Die Integrating Emitter and Photosensor
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Solution Overview
Problem
Conventional photosensors near light emitting diodes (LEDs) face challenges in maintaining consistent feedback due to positioning issues and sensitivity to ambient light, affecting accuracy and real estate usage on printed circuit boards.
Innovation Solution
The implementation of segmented LED layers, where one segment acts as a photosensor and another as an emitter, with the photosensor segment being structurally identical but smaller, allowing for efficient light transmission and internal reflection to generate a current for feedback, while being insensitive to ambient light due to narrow wavelength sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional photosensors are positioned proximate to LED die, then feedback signal can be obtained, but positioning consistency and accuracy deteriorate due to positioning issues and ambient light sensitivity
Solution Approach 1:
The patent merges the LED emitter and photosensor into a single integrated LED die structure. The LED layers are segmented to form both an emitter segment and a photosensor segment on the same die, eliminating the need for separate external photosensors and their associated positioning issues. This integration ensures consistent relative positioning while the narrow wavelength sensitivity of the segmented photosensor reduces ambient light interference.
Solution Approach 2:
The LED layers are segmented into distinct emitter and photosensor portions. This segmentation allows the photosensor to be specifically optimized for detecting the LED's own emission wavelength while maintaining structural integration. The segmented approach enables the photosensor to focus on a narrow wavelength range, reducing sensitivity to ambient light while preserving accurate feedback capability.
2Reliability
If separate photosensors are used for feedback, then LED operation can be monitored, but real estate on printed circuit board increases
Solution Approach 1:
The patent combines the LED light-emitting function and the photosensing function into a single integrated die. By forming both the emitter and photosensor segments on the same LED die, the need for separate external photosensors and their associated circuit board real estate is eliminated. The integrated structure monitors LED operation while occupying minimal space on the printed circuit board.
3Measurement precision
If photosensors are positioned consistently relative to LED die, then feedback consistency improves, but manufacturing complexity increases
Solution Approach 1:
The patent eliminates positioning complexity by merging the photosensor fabrication into the same LED layer growth process. Both the emitter and photosensor segments are formed simultaneously during epitaxial growth on the same die, ensuring inherent positioning consistency without requiring additional alignment steps or complex assembly procedures.
Solution Approach 2:
The LED layers are segmented during the epitaxial growth process itself, creating distinct emitter and photosensor regions with consistent relative positioning. This segmentation approach establishes the spatial relationship between emitter and sensor segments during manufacturing, ensuring feedback consistency while avoiding complex post-fabrication positioning operations.
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
This approach provides accurate and consistent operational feedback, enabling constant light output over time and reducing the impact of aging, thus improving LED performance and efficiency by minimizing the effects of ambient light and maintaining stable operation.
Implementation Method 1
a small portion of the light from the emitter segment is transmitted sideways into the photosensor segment, which in turn generates a current. This current is generally proportional to the light emitted by the emitter segment.
Implementation Method 2
the light from the emitter segment is transmitted into the sapphire substrate and due to internal reflection, reflected back to the photosensor segment, which in turn generates a current
Data Source
AI summary
A light emitting device comprises a detector circuit and a light emitting diode (LED) die. The LED die includes a semiconductor stack grown on a substrate. The LED includes an emitter segment formed from one segment of the semiconductor stack. The LED die includes a photosensor segment formed from another segment of the semiconductor stack. The LED die includes a segmentation layer formed between the emitter segment and the photosensor segment. The segmentation layer electrically isolates the emitter segment from the photosensor segment. The LED die includes first electrodes configured to provide power to energize the emitter segment. The LED die includes second electrodes configured to send the current to the detector circuit. The detector circuit is configured to convert the current to a signal which provides operational feedback with respect to the emitter segment.