Horizontal LED Structure for Current Spreading and Light Extraction
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Solution Overview
Problem
Conventional light-emitting diodes (LEDs) face challenges in achieving high brightness due to suboptimal light reflection and current spreading, leading to decreased luminous efficiency and poor electrical properties such as antistatic issues and excessive forward voltage.
Innovation Solution
The proposed LED structure includes a light-emitting layer, upper and lower electrodes, semiconductor layers, and a low refractive index dielectric layer surrounding the lower electrode. This configuration allows for effective current spreading through epitaxial conductive points and a current blocking layer, enhancing light extraction efficiency without blocking light emitted from the active layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the current conductive points are distributed in a point-like or strip-like manner outside the upper electrode to achieve current spreading, then the light generated by the active light-emitting layer will not be blocked by the upper electrode for brightness improvement, but the main light-emitting position will not match with the optimal reflection condition resulting in a decrease in overall luminous efficiency
Solution Approach 1:
The patent applies local quality by creating different structural zones: the lower electrode is positioned at the center to coincide with the main light-emitting position for optimal reflection, while current spreading is achieved through doped semiconductor regions and contact structures distributed in specific patterns. This spatial differentiation allows simultaneous optimization of both brightness and luminous efficiency by assigning different functions to different locations.
Solution Approach 2:
The patent transitions from two-dimensional current spreading (outside the electrode) to three-dimensional current distribution by incorporating doped semiconductor layers and contact structures at multiple depths and positions. This dimensional expansion allows current to spread through volumetric paths that do not interfere with the central light-emitting position, resolving the contradiction between current spreading and light reflection optimization.
2Ease of operation
If the distance between the active light-emitting layer and the ohmic-contact electrode is kept short (not greater than 2 microns) to improve current spreading effect, then current spreading is enhanced, but poor electrical properties such as poor antistatic properties and excessive forward voltage occur
Solution Approach 1:
The patent segments the current conduction path into multiple distinct components: doped semiconductor regions for current injection, intermediate contact structures, and the lower electrode. This segmentation allows each component to be optimized independently - the doped regions provide low-resistance current spreading while the structured contact paths maintain proper electrical properties and antistatic performance, eliminating the need to compromise between current spreading and electrical reliability.
Solution Approach 2:
The patent introduces intermediary structures (doped semiconductor layers and contact structures) between the active light-emitting layer and the ohmic-contact electrode. These intermediaries facilitate effective current spreading while maintaining proper electrical properties, acting as a bridge that resolves the contradiction between current spreading effectiveness and electrical reliability.
3Ease of operation
If a metal-contact electrode is arranged outside the upper electrode to spread the current, then current spreading is achieved, but the metal-contact electrode absorbs light and affects LED light extraction
Solution Approach 1:
The patent extracts the light-blocking function from the current-spreading structure by separating these two functions into different components. The lower electrode is positioned at the center to reflect light, while current spreading is achieved through doped semiconductor regions and contact structures that are transparent or minimally interfering with light extraction. This functional separation eliminates the harmful light absorption effect while maintaining current spreading benefits.
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 improved LED structure achieves higher brightness and luminous efficiency by optimizing light reflection and current spreading, while also addressing electrical issues such as antistatic properties and forward voltage.
Implementation Method 1
the bottom structure of the epitaxial layer of the wafer-bonded LED has the following characteristics: (1) the bottom structure of the epitaxial layer in the LED has a low refractive index dielectric layer and a reflection metal. Since the lower the refractive index value of the dielectric layer, the more total reflection will occur. Through the function of this dielectric layer and the reflection metal, the light emitted by the active light-emitting layer of the LED will be reflected upward to achieve the purpose of increasing brightness
Implementation Method 2
each of the epitaxial conductive points is a heavily doped composite layer with tunneling effect. By applying the tunneling effect based on semiconductor physics, the tunneling effect is formed from the N-type semiconductor to the P-type semiconductor under heavy doping conditions in both N-type and P-type semiconductors to achieve the dispersion of current spread away from the electrodes
Data Source
AI summary
The present invention relates to a light-emitting diode (LED) which comprises a light-emitting layer, an upper electrode, a lower electrode, a first semiconductor layer, a second semiconductor layer, a third semiconductor layer, and a low refractive index dielectric layer. The upper electrode and the lower electrode are respectively disposed on two opposite sides of the light-emitting layer. The first semiconductor layer is disposed between the light-emitting layer and the upper electrode. The second semiconductor layer is disposed between the light-emitting layer and the lower electrode. The third semiconductor layer is disposed between the second semiconductor layer and the lower electrode. The low refractive index dielectric layer is disposed to surround the lower electrode. The upper electrode is vertically overlapped with the lower electrode and the first semiconductor layer and the third semiconductor layer are electrically opposite to the second semiconductor layer.