P-side Up LED with Silicon Substrate for Light Extraction
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Solution Overview
Problem
Conventional light-emitting diodes (LEDs) face efficiency losses due to light absorption by N-type gallium arsenide substrates and processing difficulties in substrate bonding, which limits brightness and reliability.
Innovation Solution
A high efficiency LED design with a P-side up illuminant epitaxial structure and a silicon permanent substrate, featuring a transparent current-spreading layer and reduced opaque electrode area, along with a bonding process that avoids high temperature steps to enhance light extraction and electrical conductivity, using materials like PbSn, AuGe, and Si for improved bonding and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If N-type gallium arsenide substrate is used, then the substrate can support the light-emitting diode structure, but the substrate absorbs light and reduces light emitting efficiency
Solution Approach 1:
The patent extracts the light-absorbing N-type GaAs substrate from the final device structure and replaces it with a transparent substrate. The active layer is transferred to the transparent substrate through a bonding process, eliminating the harmful light absorption while maintaining structural support functionality.
Solution Approach 2:
The patent introduces a bonding layer as an intermediary between the active layer and the transparent substrate. This bonding layer facilitates the transfer and attachment of the active layer to the transparent substrate, enabling the replacement of the absorbing substrate without damaging the active layer structure.
2Strength
If high temperature bonding process is performed, then the bonding between substrates is strong, but the adhesive layer material degrades and reduces LED reliability
Solution Approach 1:
The patent changes the temperature parameter of the bonding process from high temperature to low temperature (below the melting point of the adhesive layer material). This parameter change allows achieving sufficient bonding strength while preventing degradation of the adhesive layer, thereby maintaining LED reliability.
3Ease of operation
If electrode area is increased to improve current spreading, then current distribution improves, but the opaque area increases and brightness decreases
Solution Approach 1:
The patent applies local quality by making the current spreading layer transparent in the regions where light emission is needed, while maintaining electrical conductivity. This allows the electrode to perform current spreading function locally without blocking light in the same regions, thus improving both current distribution and brightness.
Solution Approach 2:
The patent uses a composite current spreading layer that combines electrical conductivity and optical transparency. This composite material structure allows simultaneous achievement of good current spreading effect and high light transmission, resolving the contradiction between electrode function and 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
The solution increases light extraction efficiency, improves current-spreading, reduces opaque electrode area, and enhances the brightness and reliability of LEDs by using silicon substrates with high thermal and electrical conductivity, while simplifying the bonding process.
Implementation Method 1
silicon has properties of high thermal conductivity
Implementation Method 2
high electrical conductivity
Implementation Method 3
transparent current-spreading layer with a larger thickness and higher electrical conductivity
Implementation Method 4
reflective contact structure deposed on the bonding layer
Data Source
AI summary
A high efficiency light-emitting diode and a method for manufacturing the same are described. The high efficiency light-emitting diode comprises: a permanent substrate; a first contact metal layer and a second contact metal layer respectively deposed on two opposite surfaces of the permanent substrate; a bonding layer deposed on the second contact metal layer; a diffusion barrier layer deposed on the bonding layer, wherein the permanent substrate, the bonding layer and the diffusion barrier layer are electrically conductive; a reflective metal layer deposed on the diffusion barrier layer; a transparent conductive oxide layer deposed on the reflective metal layer; an illuminant epitaxial structure deposed on the transparent conductive oxide layer, wherein the illuminant epitaxial structure includes a first surface and a second surface opposite to the first surface; and a second conductivity type compound electrode pad deposed on the second surface of the illuminant epitaxial structure.