Multi-Layer Contact Configuration for Optoelectronic Devices
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Solution Overview
Problem
Semiconductor emitting devices, such as LEDs and laser diodes, face issues with light trapping due to abrupt changes in refractive index at interfaces, leading to absorption rather than emission, despite efforts to alleviate this with roughness and reflective surfaces.
Innovation Solution
An optoelectronic device with a multi-layer contact configuration, featuring a mesa and interconnected fingers, where a reflective metallic contact layer is used over an n-type semiconductor layer to enhance light extraction by reducing Fresnel losses and internal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single-layer metallic contact is used, then electrical contact is achieved, but light absorption increases and light extraction decreases
Solution Approach 1:
The contact structure is segmented into multiple functional layers: a first metallic contact layer for electrical contact and a second metallic contact layer with reflective properties for light extraction enhancement. This segmentation allows each layer to perform its specific function optimally, reducing overall light absorption while maintaining electrical conductivity.
Solution Approach 2:
The contact structure uses composite material configuration with at least two different metallic layers, where the first layer provides electrical conductivity and the second layer provides reflective properties. This composite approach combines the advantages of different materials to simultaneously achieve good electrical contact and reduced light absorption.
2Loss of energy
If light travels from high refractive index material to low refractive index material, then light extraction is improved, but total internal reflection increases causing light trapping
Solution Approach 1:
The patent converts the harmful effect of total internal reflection into a beneficial one by using the reflective properties of the second metallic contact layer to redirect trapped light back into the semiconductor layer, where it can potentially escape through other paths, thus converting light trapping into light extraction enhancement.
Solution Approach 2:
The second metallic contact layer acts as an intermediary between the semiconductor layer and the external environment, providing a reflective surface that mediates the light path and helps overcome the total internal reflection limitation by redirecting light at angles that can escape the high refractive index material.
3Loss of energy
If interface roughness is introduced to alleviate light trapping, then light extraction improves, but manufacturing complexity increases
Solution Approach 1:
Instead of modifying the semiconductor interface physically through roughening, the patent creates a functional copy of the roughness effect using a reflective metallic layer that optically mimics the light-scattering and redirecting properties of a rough interface, thereby achieving similar light extraction enhancement without the manufacturing complexity.
Solution Approach 2:
The patent replaces the mechanical approach of creating physical roughness at the interface with an optical approach using a reflective metallic layer. This substitution achieves the same light extraction benefit through optical reflection and redirection rather than through mechanical interface modification.
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 configuration improves light emission efficiency by minimizing absorption and maximizing light transmission through the use of reflective surfaces and optimized contact layers, leading to enhanced performance in devices like LEDs and laser diodes.
Implementation Method 1
a first n-type metallic contact layer located over at least a portion of the n-type contact region in proximity of the mesa boundary, wherein the first n-type metallic contact layer forms an ohmic contact with the n-type semiconductor layer
Implementation Method 2
a second metallic contact layer located over a second portion of the n-type contact region, wherein the second metallic contact layer is formed of a reflective metallic material
Implementation Method 3
An optoelectronic device with a multi-layer contact configuration, featuring a mesa and interconnected fingers, where a reflective metallic contact layer is used over an n-type semiconductor layer to enhance light extraction by reducing Fresnel losses and internal reflection
Data Source
AI summary
An optoelectronic device with a multi-layer contact is described. The optoelectronic device can include an n-type semiconductor layer having a surface. A mesa can be located over a first portion of the surface of the n-type semiconductor layer and have a mesa boundary, which has a shape including a plurality of interconnected fingers. The n-type semiconductor layer can have a shape at least partially defined by the mesa boundary. A first n-type contact layer can be located adjacent to another portion of the n-type semiconductor contact layer, where the first n-type contact layer forms an ohmic contact with the n-type semiconductor layer. A second contact layer can be located over a second portion of the n-type semiconductor contact layer, where the second contact layer is formed of a reflective material.