Semiconductor Light Emitting Device Electrode Structure for Light Extraction
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Solution Overview
Problem
Conventional semiconductor light emitting devices suffer from light absorption and degradation due to thick metallic electrodes, which reduce light extraction efficiency and are prone to rupture under power application.
Innovation Solution
A semiconductor light emitting device with a reflective layer of increased thickness and an anti-rupture layer having a lower thermal expansion coefficient, preventing rupture and enhancing light reflection and output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If thick metallic electrodes are used for current spreading, then current supply capability is improved, but light extraction efficiency deteriorates due to high absorption loss
Solution Approach 1:
The electrode structure is segmented into multiple functional layers: a reflective layer for light extraction, a protective layer for mechanical strength, and a current spreading layer for electrical conduction. This segmentation allows each layer to optimize its specific function without compromising the others, resolving the contradiction between current supply and light extraction.
Solution Approach 2:
The electrode uses a composite structure combining materials with different properties: a reflective material (such as aluminum or silver) for high light reflection, a protective material (such as silicon dioxide or silicon nitride) for mechanical strength and thermal stability, and a conductive material for current spreading. This composite approach enables simultaneous optimization of electrical and optical performance.
2Productivity
If metallic bonding pads and finger electrodes are used for current spreading, then current distribution is improved, but light absorption increases leading to energy loss
Solution Approach 1:
The current spreading function is separated from the light extraction function. The current spreading layer is positioned and designed to provide adequate current distribution, while the reflective layer above it handles light extraction, minimizing the path of light through metallic materials and reducing absorption losses.
Solution Approach 2:
The electrode structure exhibits local quality differentiation: the reflective layer has high reflectivity for light, the protective layer has appropriate thickness and material properties for mechanical protection, and the current spreading layer has optimized conductivity. Each region is tailored to its specific function, optimizing overall performance while minimizing light absorption.
3Area of stationary object
If conventional electrode structures are used in large area devices, then current spreading is facilitated, but light loss increases as light travels sideways and gets absorbed by lateral sides of electrodes
Solution Approach 1:
The solution addresses lateral light loss by adding a vertical dimension to light extraction. The reflective layer is positioned to reflect light that would otherwise travel sideways through the structure, redirecting it upward toward the light extraction surface. This dimensional approach to light management reduces lateral light loss in large area devices.
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 reduces light absorption by metallic electrodes and prevents rupture, thereby enhancing the light extraction efficiency and reliability of the semiconductor light emitting device.
Implementation Method 1
a reflective layer formed on the contact layer, while facing an exposed region of the active layer created by mesa etching and reflecting light
Implementation Method 2
the anti-rupture layer has a lower thermal expansion coefficient than that of the reflective layer, thereby preventing rupture of the reflective layer that occurs upon the application of power
Implementation Method 3
an active layer arranged between the first semiconductor layer and the second semiconductor layer and adapted to generate light by electron-hole recombination
Data Source
AI summary
Disclosed is a semiconductor light emitting device including: a plurality of semiconductor layers; and a first electrode which is formed on an exposed region of the first semiconductor layer created by mesa etching portions of the second semiconductor layer, the active layer and the first semiconductor layer, and includes a contact layer in contact with the first semiconductor layer, a reflective layer formed on the contact layer, while facing an exposed region of the active layer created by mesa etching and reflecting light, and an anti-rupture layer formed on the reflective layer.