LED With Thick Transparent Window Layer and Alloy Bonding
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Solution Overview
Problem
Conventional light-emitting diodes (LEDs) grown on insulating sapphire substrates face issues with light absorption, leading to reduced efficiency, and existing substrate bonding methods are complex and have low yield due to lattice direction consistency requirements.
Innovation Solution
A light-emitting diode with a thicker window layer made of transparent conductive material, allowing for better current spreading and easier surface roughening, and a method involving a low-fusion-point alloy for wafer bonding to enhance reliability and process flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional thin window layer is used in LED, then the device structure is simple, but the current spreading effect is poor and light extraction efficiency is low
Solution Approach 1:
The patent changes the thickness parameter of the window layer from conventional thin (typically 1-10 μm) to thick (50-200 μm). This parameter change improves current spreading effect and light extraction efficiency while maintaining device functionality. The thick window layer allows better current distribution across the active region and enhances light extraction due to increased interaction path length.
2Adaptability or versatility
If the growth substrate is removed early in the process, then the process flexibility is improved, but the structural support during subsequent steps is insufficient
Solution Approach 1:
The patent performs preliminary actions by completing all critical epitaxial growth steps and forming the thick window layer while the growth substrate is still present. The thick window layer is grown in advance to serve as a self-supporting structure. Only after the window layer reaches sufficient thickness and the growth substrate has served its purpose does the patent remove the growth substrate, enabling process flexibility without compromising structural integrity during manufacturing.
3Reliability
If a semiconductor material is used as bonding medium for wafer bonding, then the lattice matching can be achieved, but the process complexity increases and yield decreases due to lattice direction consistency requirements
Solution Approach 1:
The patent introduces a metal bonding layer as an intermediary between the LED wafer and the substrate. This metal layer serves as a mediator that eliminates the need for direct semiconductor-to-semiconductor bonding, thereby removing the stringent lattice direction consistency requirements. The metal bonding layer provides a compliant interface that accommodates lattice mismatches while maintaining reliable electrical and mechanical connections.
4Productivity
If the window layer thickness is increased to improve current spreading, then the light extraction efficiency is enhanced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent changes the window layer thickness parameter to a range of 50-200 μm, which is substantially thicker than conventional designs. This parameter change provides sufficient margin to accommodate normal manufacturing variations while ensuring adequate current spreading and light extraction performance. The increased thickness tolerance range reduces the stringency of manufacturing precision requirements compared to thin window layer designs.
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 thicker window layer improves light extraction efficiency and brightness, while the low-fusion-point alloy bonding method increases process yield and reliability by allowing more flexible bonding temperatures and wider process windows.
Implementation Method 1
a window layer deposed on the P-type semiconductor layer, wherein a thickness of the window layer is substantially at least 50 μm, and the window layer is composed of a transparent conductive material
Implementation Method 2
a reflective metal layer deposed on the metal bonding layer
Implementation Method 3
a metal bonding layer deposed on the first surface of the conductive substrate
Data Source
AI summary
A light-emitting diode (LED) and a method for manufacturing the same are described. The light-emitting diode comprises: a conductive substrate including a first surface and a second surface opposite to the first surface; a metal bonding layer deposed on the first surface of the conductive substrate; a reflective metal layer deposed on the metal bonding layer; an N-type semiconductor layer deposed on the reflective metal layer; an active layer deposed on the N-type semiconductor layer; a P-type semiconductor layer deposed on the active layer; a window layer deposed on the P-type semiconductor layer, wherein a thickness of the window layer is substantially at least 50 μm, and the window layer is composed of a transparent conductive material; and a P-type electrode deposed on the window layer.