Elongate Electrical Contacts for Uniform Current Distribution in LEDs
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Solution Overview
Problem
Semiconductor light-emitting devices, such as LEDs, face challenges in forming electrical contacts that balance current spreading and light generation area, leading to issues like current crowding and non-uniform light output due to low carrier mobility in n-type and p-type regions.
Innovation Solution
A process involving forming apertures and electrical via contacts through the semiconductor structure, with elongate contacts and interconnecting layers, and using dielectric materials to insulate and distribute current evenly, reducing current crowding and enhancing light uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a plurality of contacts are used to supply current to the inner semiconductor layer, then current spreading is improved, but the light generating area is reduced
Solution Approach 1:
The contact structure is segmented into multiple elongate contacts distributed across the semiconductor die. These contacts are arranged to provide uniform current spreading across the active layer while maintaining adequate spacing to preserve light generating area. The segmentation allows current to be distributed through multiple pathways rather than concentrated at single contact points.
Solution Approach 2:
The contact geometry and distribution are optimized locally across different regions of the semiconductor die. Each elongate contact is positioned and dimensioned to achieve uniform current density in its local region, while the overall arrangement ensures comprehensive coverage without excessive overlap that would reduce light generating area.
2Reliability
If contacts extend through the other layers of the die, then electrical contact to inner layers is achieved, but the light generating area is reduced
Solution Approach 1:
The contact structure transitions from a planar two-dimensional contact to a three-dimensional elongate contact that extends vertically through multiple layers. This dimensional change allows the contact to establish reliable electrical connection with the inner semiconductor layer while minimizing the lateral footprint on the light emitting surface, thus preserving light generating area.
Solution Approach 2:
The elongate contact is nested through the semiconductor layers, passing through the outer layers to reach the inner layer. This nested configuration allows the contact to traverse multiple functional layers without requiring separate contact openings in each layer, reducing the overall contact area while maintaining reliable electrical connection.
3Manufacturing precision
If contacts are positioned close to each other, then current spreading is enhanced, but current crowding and non-uniform light output occur
Solution Approach 1:
The elongate contacts are designed with asymmetric positioning and dimensions optimized to prevent current crowding. The contacts are arranged with non-uniform spacing patterns that account for current flow paths, ensuring adequate separation in regions where current density would otherwise concentrate, while maintaining close proximity in regions where current spreading is needed.
Solution Approach 2:
The contact arrangement and geometry are designed to create equipotential regions that promote uniform current distribution. By positioning elongate contacts to establish equipotential lines across the active layer, the design prevents current crowding at contact edges and ensures uniform current density throughout the light generating area.
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 current crowding and bright spots, achieving more uniform light output and improved reliability by ensuring equal current density across the semiconductor structure.
Implementation Method 1
insulating the sidewalls to prevent electrical contact to the second layer and the active layer by the first and second contacts
Implementation Method 2
depositing an electrically conductive material in the channel, in electrical contact with the first layer such that the first end of the first contact is spaced apart from the second contact
Data Source
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AI summary
A process for forming electrical contacts for a semiconductor light emitting apparatus is disclosed. The light emitting apparatus has a first layer of first conductivity type, an active layer for generating light overlying the first layer, and a second layer of second conductivity type overlying the active layer. The process involves forming at least a first and a second elongate electrical contact through the second layer and the active layer to provide electrical connection to the first layer, the first and second contacts oriented at an angle to each other, the first contact having a first end in proximity with the second contact, the first end being sufficiently spaced apart from the second contact such that when current is supplied to the first layer through the contacts, current contributions from the first end of the first contact and the second contact in an area generally between the first end and the second contact cause a current density in the area that is approximately equal to a current density elsewhere along the first and second contacts.