Nitride Transition Metal Via Electrodes for Flip-Chip LED Light Extraction
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Solution Overview
Problem
Flip-chip LEDs based on lateral-type LEDs suffer from reduced luminous flux and light extraction efficiency due to narrowed light emission areas, current concentration, and low optical transmittance electrodes, which hinder effective light emission and extraction.
Innovation Solution
The use of nitride transition metal via electrodes with high thermal stability and optical transmittance rates, such as CrN and TiN, minimizes active layer removal, enhances current spreading, and improves light extraction efficiency by providing a reliable and efficient light emission area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hole injection semiconductor layer and active layer are etched to form N type electrode in flip-chip LED, then electrode structure is formed, but light emission area is narrowed and luminous flux is reduced
Solution Approach 1:
The patent extracts the N type electrode formation process from the active layer etching, instead forming the N type electrode separately on the substrate before bonding. This eliminates the need to etch through the active layer, preserving the light emission area while still achieving proper electrode structure formation.
Solution Approach 2:
The N type electrode is formed preliminarily on the substrate before the active layer is transferred to the chip. This preliminary formation allows the electrode to be established without compromising the subsequent light emission area, as the electrode formation occurs before the active layer positioning.
2Ease of manufacture
If flip-chip LED is based on lateral-type LED, then manufacturing is simplified, but carrier flow is not spread and current is concentrated
Solution Approach 1:
The patent transitions from a lateral-type current flow to a vertical-type current flow by stacking the N type electrode, active layer, and P type electrode in vertical layers. This dimensional change enables current spreading through the vertical structure while maintaining manufacturing simplicity through the flip-chip bonding process.
3Reliability
If electrode with low optical transmittance rate is used, then electrical conductivity is achieved, but light is reflected and extraction efficiency is lowered
Solution Approach 1:
The patent applies different material properties to different parts of the electrode structure. The N type electrode uses nitride transition metal with high optical transmittance for light extraction, while the P type electrode uses conventional materials for electrical conductivity. This local differentiation resolves the contradiction between electrical conductivity and light extraction efficiency.
Solution Approach 2:
The patent employs composite electrode structures where the N type electrode combines nitride transition metal materials that provide both electrical conductivity and high optical transmittance. This composite approach allows simultaneous achievement of reliable electrical connection and efficient light extraction.
4Reliability
If conventional electrode materials are used, then electrical connection is established, but thermal stability is insufficient
Solution Approach 1:
The patent changes the material parameter of the N type electrode from conventional metals to nitride transition metals, which have significantly higher thermal stability. This parameter change maintains electrical connection reliability while dramatically improving thermal stability to withstand LED operating temperatures.
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 implementation of nitride transition metal via electrodes in flip-chip LEDs ensures improved luminous flux and light emission efficiency through enhanced light extraction and current spreading, resulting in a more reliable and efficient light emitting device.
Implementation Method 1
a first via electrode to make contact with the first conductive semiconductor layer through a via hole penetrating the substrate; and a second via electrode contacted with the second conductive semiconductor layer through a second via hole penetrating the substrate
Implementation Method 2
The use of nitride transition metal via electrodes with high thermal stability and optical transmittance rates, such as CrN and TiN, minimizes active layer removal, enhances current spreading, and improves light extraction efficiency
Data Source
AI summary
A light emitting device package, and a lighting system includes a light emitting device. The light emitting device includes a substrate, a first conductive semiconductor layer on the substrate, an active layer on the first conductive semiconductor layer, and a second conductive semiconductor layer on the active layer. A first via electrode contacts the first conductive semiconductor layer through a via hole formed through the substrate, and a second via electrode contacts the second conductive semiconductor layer through a second via hole formed through the substrate, the first conductive semiconductor layer, and the active layer.