Deep UV LED Mesa Structure for Current Spreading and Lower Voltage
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Solution Overview
Problem
Conventional deep UV light emitting diodes (LEDs) suffer from low light output and high forward voltage due to poor current spreading and light absorption in the p-type and n-ohmic contact layers.
Innovation Solution
A deep UV LED with a novel structure featuring a mesa with elongated rectangular shape and parallel vias exposing a first conductivity type semiconductor layer, along with a symmetrical structure to improve current spreading and light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the mesa width is increased to improve light emission area, then light output is improved, but current spreading performance deteriorates and forward voltage increases
Solution Approach 1:
The patent divides the mesa structure into multiple segments by introducing recesses at regular intervals along the light emission surface. This segmentation allows current to be injected at multiple discrete locations rather than a single point, improving current spreading across the enlarged mesa area while maintaining low forward voltage.
Solution Approach 2:
The patent transitions from a conventional planar mesa structure to a three-dimensional structured mesa with recesses. By adding vertical depth variations (recesses) to the otherwise flat surface, the patent enables both large lateral area and effective current distribution paths, resolving the contradiction between area and current spreading.
2Area of moving object
If the mesa width is increased to improve light emission area, then light output is improved, but forward voltage becomes high
Solution Approach 1:
By segmenting the mesa into multiple regions with recesses, the patent reduces the distance current must travel through high-resistance layers. Current can be injected at multiple recess locations simultaneously, reducing overall forward voltage while maintaining large emission area.
Solution Approach 2:
The patent applies different structural characteristics to different regions of the mesa. The recesses create localized areas with improved electrical characteristics, allowing current to bypass high-resistance regions and reducing forward voltage specifically where needed, while the overall large mesa area maintains high light output.
3Ease of manufacture
If a conventional mesa structure is used, then manufacturing is simple, but light output is low and forward voltage is high
Solution Approach 1:
The recess structure can be fabricated using standard semiconductor processing techniques such as photolithography and etching, which are already commonly used in LED manufacturing. The segmentation pattern is designed to be compatible with existing production lines, maintaining ease of manufacture while significantly improving light output and electrical characteristics.
Solution Approach 2:
The patent optimizes specific parameters of the recess structure (depth, width, spacing, pattern) to achieve the desired balance between manufacturing simplicity and performance improvement. By carefully selecting these parameters within practical ranges, the patent maintains compatibility with conventional manufacturing processes while achieving superior light output.
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 novel structure enhances current spreading and light output, reducing the forward voltage and improving the overall electrical and optical performance of the deep UV LED.
Implementation Method 1
an active layer... sandwiched between the n-type semiconductor layer and the p-type semiconductor layer
Data Source
AI summary
A deep UV light emitting diode includes a substrate, an n-type semiconductor layer located on the substrate, a mesa disposed on the n-type semiconductor layer, and including an active layer and a p-type semiconductor layer, an n-ohmic contact layer in contact with the n-type semiconductor layer, a p-ohmic contact layer in contact with the p-type semiconductor layer, an n-bump electrically connected to the n-ohmic contact layer, and a p-bump electrically connected to the p-ohmic contact layer. The mesa includes a plurality of vias exposing a first conductivity type semiconductor layer.