Stepped Semiconductor Layer for Laser Lift-Off Damage Prevention
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Solution Overview
Problem
Existing light emitting devices using III-V nitride semiconductors face damage during substrate separation processes, which can lead to defects and reduced reliability.
Innovation Solution
A light emitting device with a stepped structure in the first conductive type semiconductor layer, an insulating layer on the lateral surface, and a protective layer on the periphery, along with a method involving an absorption layer and laser lift-off process to separate the substrate, preventing damage and enhancing light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional planar semiconductor layer structure is used, then the device structure is simple, but the semiconductor layer is damaged during substrate separation process
Solution Approach 1:
The first conductive type semiconductor layer is divided into a stepped structure with multiple levels (first level, second level, third level) at the peripheral portion. This segmentation creates distinct regions that prevent damage propagation during substrate separation, as the stepped configuration distributes mechanical stress across multiple surfaces rather than a single planar interface.
Solution Approach 2:
The invention transitions from a two-dimensional planar semiconductor layer to a three-dimensional stepped structure by adding vertical height variations. The stepped configuration introduces a height dimension (H1, H2, H3) that provides mechanical compliance and stress distribution during substrate separation, preventing damage to the active layer.
2Illumination intensity
If the entire semiconductor layer surface is made reflective, then light extraction efficiency is maximized, but device complexity increases
Solution Approach 1:
Reflective structures are applied selectively only to the peripheral portions of each semiconductor layer (first, second, and third conductive type layers) rather than the entire surface. This local application of reflectivity enhances light extraction at the edges where it is most beneficial, while maintaining structural simplicity in the central active region.
Solution Approach 2:
Instead of applying reflectivity uniformly across the entire semiconductor layer surface, the invention applies partial reflectivity only to specific peripheral regions. This partial action is sufficient to improve light extraction efficiency without the complexity and cost of full-surface treatment.
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 effectively prevents substrate separation-induced damage, improves light extraction efficiency, and enhances the reliability of the light emitting device.
Implementation Method 1
forming an absorption layer at a peripheral portion of a top surface of a substrate, wherein the absorption layer includes a material having a band gap energy lower than that of the substrate
Data Source
AI summary
Disclosed are a light emitting device. The light emitting device includes a light emitting structure including a first and second conductive semiconductors, and an active layer; an insulating layer on a lateral surface of the light emitting structure; an electrode on the first conductive semiconductor layer; an electrode layer under the second conductive semiconductor layer; and a protective layer including a first portion between the light emitting structure and the electrode layer and a second portion extending outward beyond a lower surface of the light emitting structure, wherein the first conductive semiconductor layer includes a first top surface including a roughness on a first region, and a second top surface lower than the first region and being closer the lateral surface of the light emitting structure than the first region, wherein the second top surface is disposed on an edge portion of the first conductive semiconductor layer.