Semiconductor Light Emitting Device Omnidirectional Reflector
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Solution Overview
Problem
Flip chip light emitting devices face reduced light extraction efficiency due to metallic electrodes absorbing rather than reflecting light.
Innovation Solution
A semiconductor light emitting device with a light emitting structure including a first and second conductivity-type semiconductor layer, an active layer, a lower insulating layer with through-holes to expose the semiconductor layers, and a connection layer that implements an omnidirectional reflector structure to enhance light reflection and extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metallic electrodes are used to apply power to P/N semiconductor layers, then electrical connection is achieved, but light extraction efficiency decreases due to light absorption
Solution Approach 1:
The electrode structure is segmented into multiple functional layers: a reflective base layer (Al or Ag) for light reflection, an intermediate adhesion layer (Ti or Cr), and a terminal conductive layer (Al or Cu). This segmentation allows each layer to perform its specific function optimally while collectively achieving both electrical connection and light reflection.
Solution Approach 2:
The electrode uses composite material structure combining metals with different properties: Al/Ag for high reflectivity and conductivity, Ti/Cr for adhesion, and appropriate terminal materials for electrical connection. This composite approach resolves the contradiction by integrating materials that collectively provide both electrical functionality and optical reflection.
2Reliability
If metallic electrodes cover the entire semiconductor layer, then electrical connection is ensured, but reflection loss increases
Solution Approach 1:
The reflective property is applied locally at the electrode-semiconductor interface where it is most needed for light extraction, while the electrode maintains its electrical connection function in terminal regions. The reflective layer is positioned specifically to reflect light that would otherwise be absorbed, without compromising electrical connectivity.
3Ease of manufacture
If traditional metallic electrode structure is used, then manufacturing is simplified, but light extraction efficiency is reduced
Solution Approach 1:
The electrode is divided into sequentially deposited layers that can be manufactured using standard sputtering or evaporation techniques. Each layer is deposited in sequence (reflective layer first, then adhesion layer, then terminal layer), maintaining compatibility with existing manufacturing processes while achieving superior optical and electrical performance.
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 improves light extraction efficiency by reducing reflection loss and enhancing light reflection across all incident angles, compared to traditional designs where metallic electrodes cover the entire semiconductor layer.
Implementation Method 1
an omnidirectional reflector structure to enhance light reflection and extraction efficiency
Data Source
AI summary
A semiconductor light emitting device includes a light emitting structure including a first conductivity-type semiconductor layer, an active layer, and a second conductivity-type semiconductor layer; and an insulating layer on the light emitting structure and including first and second through-holes. The insulating layer includes a first lower insulating layer and a second lower insulating layer. The first insulating layer is disposed on the first conductivity-type semiconductor layer and is surrounded by the second lower insulating layer with the first through-hole interposed therebetween.