Columnar LED Sidewall Reflectors for Main-Surface Light Extraction
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Solution Overview
Problem
In semiconductor light emitting elements with columnar semiconductor layers, the light emitted tends to be extracted in the in-plane direction rather than the main surface direction, leading to reduced external quantum efficiency due to absorption by other columnar layers.
Innovation Solution
A side surface reflection portion is introduced on the columnar semiconductor layers, using a light reflection film such as a metal or dielectric multilayer film to reflect light emitted from the active layer perpendicular to the growth substrate, increasing light extraction in the main surface direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If columnar semiconductor layers are used to reduce crystal defects, then crystal quality is improved, but light extraction in main surface direction deteriorates
Solution Approach 1:
The invention introduces a side surface reflection portion on the lateral surface of the columnar semiconductor layer to redirect light that would otherwise be extracted in the in-plane direction. This adds a reflective dimension to the light extraction path, converting horizontally-traveling light into vertically-directed light that exits through the main surface, thereby resolving the contradiction between maintaining columnar structure for crystal quality and achieving efficient main-surface light extraction.
2Power
If active layer is formed along side surface of columnar semiconductor layer, then external quantum efficiency in high current density is improved, but light absorption by other columnar layers increases
Solution Approach 1:
The side surface reflection portion extracts light from the in-plane propagation path before it can be absorbed by adjacent columnar semiconductor layers. By placing the reflection portion on the side surface, light generated in the active layer is redirected upward toward the main surface extraction path, removing it from the harmful horizontal propagation path where absorption by neighboring columns would occur.
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 configuration enhances light extraction in both the main surface and back surface directions, improving external quantum efficiency by reflecting and redirecting light emitted from the active layer.
Implementation Method 1
a side surface reflection portion configured to reflect at least a part of light emitted from the columnar semiconductor layer is provided on a side surface of the columnar semiconductor layer
Data Source
AI summary
Please delete the abstract now appearing in the currently filed specification and add the following new paragraph as the abstract:A semiconductor light emitting element includes: a growth substrate; a plurality of columnar semiconductor layers on the growth substrate; a side surface reflection portion provided on a side surface of the columnar semiconductor layer; and an embedded layer covering the columnar semiconductor layer and the side surface reflection portion. The side surface reflection portion is configured to reflect at least a part of light emitted from the columnar semiconductor layer.