LED Contact Structures Sidewall Interconnects Current Spreading
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Solution Overview
Problem
Solid-state lighting devices, such as LEDs, face limitations in light emission efficiency due to internal reflection and current spreading issues, which hinder the extraction of light and overall brightness, especially in larger area LEDs.
Innovation Solution
The development of contact structures for LED chips that allow electrical connections outside the lateral boundaries of the active LED structure, including n-contact and p-contact interconnect configurations that extend across or cover areas of the active structure, improving current spreading and light extraction without reducing the active LED area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If contact structures are placed within the active LED structure area, then electrical connections are achieved, but the active area is reduced and current spreading is limited
Solution Approach 1:
The contact structures are extended into the third dimension by forming them on the sidewalls of the active LED structure. The n-contact and p-contact are positioned on opposite sidewalls, allowing electrical connections without occupying lateral active area. This vertical/sidewall positioning resolves the contradiction by moving contacts from the 2D plane to 3D space.
Solution Approach 2:
Conductive layers are introduced as intermediary elements to establish electrical connections between the contacts and the semiconductor layers. The n-contact connects to the n-type layer through a conductive layer, and the p-contact connects to the p-type layer through another conductive layer, enabling reliable current spreading without direct contact occupation of active area.
2Illumination intensity
If internal reflective surfaces are added to enhance light extraction, then light extraction efficiency improves, but device complexity increases
Solution Approach 1:
The substrate surface is textured or patterned to change the optical parameters at the light extraction interface. This surface modification increases light extraction efficiency by reducing internal reflection, achieved through physical or chemical etching processes that create micro-scale surface features without adding complex internal reflective structures.
Solution Approach 2:
The substrate itself provides the light extraction enhancement through its inherent optical properties and surface characteristics. The substrate is designed with appropriate refractive index and surface texture to naturally facilitate light extraction, eliminating the need for additional reflective layers or complex internal structures.
3Illumination intensity
If larger area LEDs are used to increase brightness, then light output increases, but current spreading becomes insufficient
Solution Approach 1:
The contact structures are divided into multiple segments positioned at different locations around the active LED structure. The n-contact and p-contact are segmented and placed on different sidewalls, creating multiple current injection points that improve current spreading across the larger active area without compromising brightness.
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 configuration enhances light extraction and current spreading, leading to improved brightness and efficiency in LED chips by minimizing the impact on active areas and optimizing light transmission.
Implementation Method 1
n-contact interconnect configurations that form electrical connections between n-contacts and n-type layers of LED chips outside of lateral boundaries of the active LED structures
Implementation Method 2
it has been found useful to pattern, roughen, or otherwise texture the interface between an LED surface and the surrounding environment to provide a varying surface that increases the probability of refraction over internal reflection and thus enhances light extraction
Implementation Method 3
Light extraction and external quantum efficiency of an LED can be limited by a number of factors, including internal reflection
Implementation Method 4
When a bias is applied across the doped layers, holes and electrons are injected into the one or more active layers where they recombine to generate emissions such as visible light or ultraviolet emissions
Data Source
AI summary
Solid-state lighting devices including light-emitting diodes (LEDs) and more particularly contact structures for LED chips are disclosed. LED chips as disclosed herein may include contact structure arrangements that have reduced impact on areas of active LED structures within the LED chips. Electrical connections between an n-contact and an n-type layer may be arranged outside of a perimeter edge or a perimeter corner of the active LED structure. N-contact interconnect configurations are disclosed that form electrical connections between n-contacts and n-type layers of LED chips outside of lateral boundaries of the active LED structures. By electrically contacting n-type layers outside of the lateral boundaries of the active LED structures, LED chips are provided with improved current spreading and improved brightness.