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 optical properties at interfaces, leading to significant light absorption and reduced light extraction efficiency.
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 a portion of the n-type contact region to form an ohmic contact with the semiconductor layer, reducing light absorption and enhancing light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional single-layer metallic contact is used, then electrical conductivity is achieved, but light absorption increases and light extraction efficiency decreases
Solution Approach 1:
The contact structure is divided into multiple functional layers: a first metallic contact layer providing ohmic contact and electrical conductivity, and a second metallic contact layer providing reflectivity. This segmentation allows each layer to perform its specialized function, reducing overall light absorption while maintaining electrical performance.
Solution Approach 2:
The contact structure uses a composite of different metallic materials with complementary properties. The first layer uses a metal with good ohmic contact properties, while the second layer uses a highly reflective metal. This composite structure combines the advantages of both materials to reduce light absorption and improve light extraction efficiency.
2Loss of energy
If light travels from high refractive index semiconductor to low refractive index medium, then light extraction is possible, but total internal reflection traps a large fraction of light
Solution Approach 1:
The patent converts the harmful effect of total internal reflection into a beneficial one by using the reflective metallic contact layer to reflect trapped light back into the semiconductor layer. This reflected light can then be extracted through other pathways, transforming the light-trapping problem into a light-redirection solution that improves overall extraction efficiency.
3Loss of energy
If interface roughness is increased to alleviate light trapping, then some light can escape without total internal reflection, but Fresnel losses still reflect a significant fraction of transmitted light
Solution Approach 1:
The reflective metallic contact layer acts as an intermediary that captures light which would otherwise be lost to Fresnel reflections. By positioning this reflective layer at the contact region, it intercepts and redirects light that encounters the semiconductor-metal interface, reducing the impact of Fresnel losses without requiring changes to the interface quality.
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 light trapping and absorption, allowing a larger fraction of emitted light to be transmitted and reducing Fresnel losses.
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
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. An n-type contact region can be located over a second portion of the surface of the n-type semiconductor contact layer entirely distinct from the first portion, and be at least partially defined by the mesa boundary. A first n-type metallic contact layer can be located over at least a portion of the n-type contact region in proximity of the mesa boundary, where the first n-type metallic contact layer forms an ohmic contact with the n-type semiconductor layer. A second metallic contact layer can be located over a second portion of the n-type contact region, where the second metallic contact layer is formed of a reflective metallic material.