Roughened Contact Layer Structure for Higher LED Light Extraction
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Solution Overview
Problem
The manufacturing of optoelectronic devices, particularly thin-film LEDs and infrared LEDs, is hindered by suboptimal roughening across multiple layers, leading to inefficient light coupling and increased costs due to complex and costly processes.
Innovation Solution
An optoelectronic device structure comprising a first current spreading layer, an active layer, a second current spreading layer, a contact layer, and a roughening layer, where the roughening layer is positioned on top of the contact layer and has a roughened surface to enhance light coupling, and a method involving surface roughening and selective doping to reduce light absorption and improve efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If roughening is performed over several layers of different composition, then light coupling efficiency may be improved through multiple interfaces, but the roughening structure deviates from optimal and manufacturing complexity increases
Solution Approach 1:
The invention extracts the roughening function from multiple composite layers and concentrates it into a single dedicated roughening layer. This single layer is positioned between the contact layer and the current spreading layer, performing the entire light coupling function at one location rather than distributing it across multiple layers with different compositions.
Solution Approach 2:
The roughening layer serves multiple functions simultaneously: it provides the optimal roughened surface for light coupling, maintains electrical contact integrity, and simplifies the overall layer structure. By making this single layer universal in its functionality, the invention avoids the complexity of coordinating multiple specialized layers.
2Use of energy by moving object
If a separate contact layer and roughening layer are used, then light coupling is enhanced, but manufacturing process complexity increases
Solution Approach 1:
The invention merges the contact layer and roughening layer into a single integrated layer structure. The roughening layer is deposited directly on the contact layer, combining electrical contact functionality with light coupling functionality in one continuous structure, thereby simplifying the manufacturing process while maintaining enhanced light emission efficiency.
3Reliability
If the roughening layer is highly doped to improve electrical contact, then electrical conductivity increases, but light absorption increases reducing emission efficiency
Solution Approach 1:
The invention applies local quality by creating different doping levels in different regions of the contact layer. The region underlying the roughening layer is heavily doped to ensure excellent electrical contact and low resistance, while the region extending into the roughening layer has reduced doping to minimize light absorption. This spatial variation in doping quality allows simultaneous optimization of both electrical and optical properties.
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 allows for cost-effective manufacturing by simplifying the process, reducing light absorption, and enhancing the morphology of epitaxial layers, resulting in improved light emission efficiency and increased yields.
Implementation Method 1
The roughening layer has a roughened surface from which the light generated in the active layer is coupled out
Implementation Method 2
Charge carriers or electron/hole pairs can recombine in the active layer. The energy released during recombination is at least partially emitted as light, i.e. as a photon
Data Source
AI summary
The invention relates to an optoelectronic device including a first current spreading layer made of a semiconductor material of a first conductivity type, an active layer which is arranged on the first current spreading layer for generating light, a second current spreading layer which is arranged on the active layer and is made of a semiconductor material of a second conductivity type, a contact layer which is arranged on the second current spreading layer, a roughened layer which is arranged on the contact layer and comprises a roughened surface for coupling out light generated in the active layer, and a metal layer which is arranged on the contact layer.