Semiconductor Light Emitting Device Acute Etched Surfaces
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Solution Overview
Problem
Conventional semiconductor light-emitting devices suffer from poor light distribution uniformity and reduced light extraction efficiency due to the geometry of their etched surfaces, which leads to high light intensity at specific emission angles and reduced intensity towards others, resulting in inefficient light emission.
Innovation Solution
The semiconductor light-emitting device features a substrate with a patterned surface and an epitaxial structure that includes non-parallel etched surfaces formed through a combination of epitaxial growth and wet-etching processes, specifically using orthophosphoric acid to create acute angles between the etched surfaces and the exposed surface, enhancing light extraction and distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional etched surfaces with single angle are used, then manufacturing process is simple, but light distribution uniformity is poor and light extraction efficiency is reduced
Solution Approach 1:
The patent applies asymmetry by creating non-parallel etched surfaces with different angles (first angle and second angle) on the sidewalls of the semiconductor light-emitting device. This asymmetric geometry redirects light rays that would normally undergo total internal reflection at uniform angles, scattering them in multiple directions to achieve more uniform light distribution across the emission pattern.
Solution Approach 2:
The patent transitions from a single-angle etched surface (one-dimensional control) to multi-angle etched surfaces (two-dimensional control of light redirection). By introducing varying angles on different sidewalls, the patent adds dimensional complexity to light path control, enabling rays to be redirected along different trajectories for improved angular distribution.
2Device complexity
If conventional single-angle etched surfaces are used, then device structure is simple, but light extraction efficiency is reduced due to total internal reflection
Solution Approach 1:
The asymmetric multi-angle etched surfaces prevent uniform total internal reflection by creating varied incident angles for light rays at the semiconductor-air interface. This asymmetry allows more rays to fall below the critical angle for total internal reflection, thereby improving light extraction efficiency despite increased geometric complexity.
Solution Approach 2:
The patent changes the geometric parameters of the etched surfaces by introducing multiple angles instead of a single uniform angle. This parameter variation modifies the light-ray interaction characteristics, reducing energy loss through total internal reflection and improving overall light extraction efficiency.
3Illumination intensity
If non-parallel etched surfaces with multiple angles are used, then light distribution uniformity is improved, but manufacturing process complexity increases
Solution Approach 1:
The patent employs preliminary action by performing selective wet-etching on specific crystallographic facets of the semiconductor sidewalls before final device assembly. The etching process is designed to naturally form the desired multi-angle geometry through controlled chemical reactions with the semiconductor material, establishing the light-redistributing structure in advance of other manufacturing steps.
Solution Approach 2:
The wet-etching process utilizes the self-service principle by leveraging the inherent crystallographic structure and chemical reactivity of the semiconductor material to automatically form the desired non-parallel etched surfaces. The etchant selectively removes material based on crystal orientation, self-organizing into the multi-angle geometry needed for light redistribution without requiring complex external control mechanisms.
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 improves light distribution uniformity by directing light rays to emit at broader angles (60° to 120°) with reduced absorption, resulting in increased optical power output and enhanced light extraction efficiency compared to conventional devices.
Implementation Method 1
a bottom part of the first type semiconductor layer, the buffer layer and the nucleation layer includes a second sidewall including a second etched surface so that a second angle between the second etched surface and the exposed surface is also acute
Data Source
AI summary
A semiconductor light emitting device includes a substrate having a main surface and an exposed surface; an epitaxial structure, disposed on the main surface of the substrate, having at least a first type semiconductor layer, a light-emitting layer, and a second type semiconductor layer, wherein the first type layer has a first sidewall including at least a first etched surface and a second etched surface, wherein angles between the etched surfaces and the exposed surface are acute angles; and an electrode structure disposed on the epitaxial structure.