Flip-Chip LED Window Layer Doping for Current Spreading and Light Output
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Solution Overview
Problem
Existing light emitting diodes (LEDs) face challenges in preventing light loss at the P-electrode pad while improving heat dissipation efficiency, particularly in large-area flip-chip type LEDs, and there is a need for improved current spreading and luminous efficacy.
Innovation Solution
A light emitting module with a first window layer having a high-level doped layer for efficient electron supply, cladding layers to regulate electron and hole flow, and a reflective layer to enhance light emission, along with individually controllable light emitting devices of varying peak wavelengths and a molding layer to compensate for height differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a reflective electrode is formed on the P-type semiconductor layer and extensions for current spreading are formed in an exposed region of the N-type semiconductor layer, then current spreading is improved, but light loss at the P-electrode pad increases
Solution Approach 1:
The P-type semiconductor layer is segmented into a light-emitting region and a non-light-emitting region. The non-light-emitting region is positioned beneath the P-electrode pad to prevent light loss, while the light-emitting region maintains extensions for current spreading. This segmentation allows the P-type layer to simultaneously support both current distribution and light emission functions without compromising luminous efficacy.
2Temperature
If the area of the light emitting device is increased to improve heat dissipation, then heat dissipation efficiency is improved, but light loss at the electrode pad increases
Solution Approach 1:
The P-type semiconductor layer is designed with spatially varying properties: the region beneath the P-electrode pad has non-light-emitting characteristics to prevent light loss, while other regions maintain light-emitting characteristics. This local quality differentiation allows large-area devices to achieve improved heat dissipation while maintaining high luminous efficacy in the light-emitting regions.
3Productivity
If a high doping level is applied to the first window layer to improve electron supply, then electron supply efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The first window layer is doped at a high level (4×10^18 atoms/cm³ or higher) to enhance electron supply efficiency to the active layer. This parameter change in doping concentration significantly improves carrier injection efficiency while remaining compatible with standard semiconductor fabrication processes, thus achieving high productivity without excessive manufacturing complexity.
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 improves luminous efficacy, allows for high brightness and single-color light sources, and facilitates convenient circuit construction with uniform mesa directions across different color LEDs, enabling flexible module arrangements.
Implementation Method 1
a first high-level doped layer having a higher doping level applied than other portions of the first window layer
Implementation Method 2
an active layer disposed between the first window layer and the second window layer
Implementation Method 3
a first cladding layer disposed between the first window layer and the active layer to prevent the holes from crossing over into the first window layer
Data Source
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AI summary
A light emitting module is disclosed. The light emitting module includes a light emitting device, and the light emitting device including: a substrate; a first window layer supplying electrons; a second window layer supplying holes; an active layer disposed between the first window layer and the second window layer; a first ohmic electrode electrically connected to the first window layer; and a second ohmic electrode electrically connected to the second window layer, wherein the first window layer includes a first high-level doped layer having a higher doping level applied than other portions thereof and wherein the first ohmic electrode is electrically connected to the first high-level doped layer.