Reflective Electrode for Semiconductor Light Emitting Apparatus
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Solution Overview
Problem
Existing semiconductor light-emitting devices face challenges in finding a metal for reflective electrodes that provides good electrical contact, high reflectivity, and adhesion to semiconductor materials, leading to reduced efficiency due to light attenuation.
Innovation Solution
A process involving the deposition of an intermediate electrically conductive layer that diffuses into the cladding layer, followed by a reflective layer, which is electrically conductive and in contact with the intermediate layer, to form a reflective electrode that minimizes light attenuation while maintaining good ohmic contact and reflectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal layer is used to provide good electrical contact and adhesion to the semiconductor material, then electrical contact and adhesion are improved, but light reflectivity is reduced due to significant light attenuation
Solution Approach 1:
The reflective electrode is divided into multiple functional layers: a first intermediate layer (e.g., Ti, Cr, Al) deposited on the semiconductor layer to provide adhesion and electrical contact, a second intermediate layer (e.g., Mo, W, Pt) deposited on the first intermediate layer to provide reflectivity while maintaining electrical contact, and optionally a protective layer. This segmentation allows each layer to optimize for its specific function without compromising the others.
Solution Approach 2:
The reflective electrode uses composite material structure combining different metals with complementary properties. The first intermediate layer provides adhesion to semiconductor, the second intermediate layer provides high reflectivity and maintains electrical conductivity. This composite approach achieves the sum of individual layer benefits while minimizing the drawbacks of any single material.
2Reliability
If a plurality of layers are used to make up the reflective electrode to provide good adhesion, electrical contact, and reflectivity, then adhesion and electrical contact are improved, but light attenuation increases due to multiple interfaces and material thickness
Solution Approach 1:
Each layer in the reflective electrode structure is optimized for its specific local function: the first intermediate layer is optimized for adhesion to the semiconductor layer, the second intermediate layer is optimized for reflectivity and electrical contact. By assigning different qualities to different parts (layers), the structure achieves overall performance without requiring excessive thickness in any single layer, thus reducing total light attenuation.
Solution Approach 2:
The patent optimizes the thickness parameters of each intermediate layer to achieve the desired balance between electrical contact, adhesion, and light reflectivity. By carefully controlling layer thicknesses (typically in the range of nanometers to a few micrometers), the structure provides sufficient electrical conductivity and mechanical adhesion while minimizing light absorption and scattering losses.
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 approach enhances the reflectivity and reduces forward voltage drop, improving the overall efficiency of semiconductor light-emitting devices by allowing the use of conductive materials with higher reflectivity without significant light attenuation.
Implementation Method 1
causing at least a portion of the electrically conductive material to diffuse into the cladding layer
Implementation Method 2
Causing at least the portion of the electrically conductive material to diffuse into the cladding layer may involve annealing the light emitting device
Implementation Method 3
a reflective layer on the intermediate layer, the reflective layer being electrically conductive and in electrical contact with the intermediate layer
Data Source
Figure 1
Figure 2
Figure 3A~3E
AI summary
A process is disclosed for forming a reflective electrode on a semiconductor light emitting device, the light emitting device having an active layer (16) for generating light and a cladding layer (18) in electrical contact with the active layer. The process involves depositing an intermediate layer (24) of electrically conductive material on the cladding layer and causing at least a portion of the electrically conductive material to diffuse into the cladding layer. The process further involves depositing a reflective layer (26) on the intermediate layer, the reflective layer being electrically conductive and in electrical contact with the intermediate layer.