LED Chip Wavelength Converting Layer and DBR Design
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Solution Overview
Problem
Existing LED technologies face challenges in achieving uniform wavelength conversion and light emission efficiency, particularly when light is emitted through side surfaces, and in preventing damage to wavelength converting layers from emitted light.
Innovation Solution
The development of an LED chip with a wavelength converting layer that covers both top and side surfaces, incorporating a spacer layer and a distributed Bragg reflector (DBR) to manage light emission and prevent light from being incident back into the chip, allowing for efficient wavelength conversion and wire bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a wavelength converting sheet is attached on the top surface of the LED, then white light can be implemented at a chip level, but it is limited to LEDs where light is mostly emitted through the top surface and cannot effectively convert light emitted through side surfaces
Solution Approach 1:
The wavelength converting layer is extended from a two-dimensional top surface attachment to a three-dimensional structure that covers both the top surface and side surfaces of the LED chip. This dimensional expansion allows the conversion function to capture light emitted in multiple directions, making the solution adaptable to different LED emission configurations including those with significant side surface emission.
2Ease of operation
If a resin containing phosphor is applied in the package, then wire bonding can be performed without issue, but the phosphor cannot be uniformly distributed and uniform thickness is difficult to achieve
Solution Approach 1:
The wavelength converting layer is formed on the LED chip surface before wire bonding is performed. This preliminary formation of the conversion layer eliminates the need to apply phosphor-containing resin afterward, thereby ensuring uniform thickness and distribution while still allowing subsequent wire bonding operations to proceed without interference.
3Reliability
If a wavelength converting layer is formed at the chip level, then wavelength conversion can be achieved, but wire bonding becomes difficult because electrodes may be covered by the converting layer
Solution Approach 1:
The wavelength converting layer is selectively formed to cover specific regions of the LED chip surface while leaving electrode areas exposed or accessible. This localized quality differentiation allows the conversion layer to perform its function over the light-emitting surfaces while maintaining electrode accessibility for wire bonding operations.
4Productivity
If the wavelength converting layer is placed close to the light source, then conversion efficiency is improved, but the layer may be damaged by the emitted light
Solution Approach 1:
A spacer layer is introduced as an intermediary element positioned between the light-emitting semiconductor stacked structure and the wavelength converting layer. This spacer maintains a controlled distance that prevents direct light damage to the converting layer while still allowing efficient optical coupling for wavelength conversion, thus protecting the converting layer from degradation.
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 solution enables effective wavelength conversion for light emitted through both top and side surfaces, enhances light emission efficiency, and protects the wavelength converting layer from damage, improving the overall performance of LED chips.
Implementation Method 1
a distributed Bragg reflector (DBR) to manage light emission and prevent light from being incident back into the chip
Implementation Method 2
white light is implemented through the combination of an InGaN LED to emit blue light of 430 nm to 470 nm and a phosphor to covert the blue light into light of a longer wavelength
Data Source
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AI summary
An exemplary embodiment of the present invention discloses an LED chip including a substrate (21), a GaN-based compound semiconductor stacked structure (30) arranged on the substrate, an electrode (42) electrically connected to the semiconductor stacked structure, and a wavelength converting layer (50) covering a portion of the semiconductor stacked structure. The electrode passes through the wavelength converting layer. The semiconductor stacked structure includes a first conductivity-type semiconductor layer (25), an active layer (27), and a second conductivity-type semiconductor layer (29).