Vertical LED Ohmic Contact via Polarity-Specific Electrode Layers

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Solution Overview

Problem

Vertical-type LEDs face challenges in forming a superior ohmic contacting interface, leading to high driving voltage drops and reduced lifespan due to differences in electrode material behavior on surfaces with group-III metallic and nitrogen polarities.

Innovation Solution

A light emitting device structure featuring a support substrate, wafer bonding layers, a current spreading layer, a second conductive semiconductor layer, an active layer, a first conductive semiconductor layer with a surface modification layer, and a first electrode layer, which forms a superior ohmic contacting interface by using materials like Au, Ag, or Rh for the current spreading and bonding layers and In2S3 or Ga2O3 for the surface modification layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the same electrode material (Ti/Al) is stacked on both gallium polarity and nitrogen polarity surfaces, then manufacturing process is simplified, but superior ohmic contacting interface cannot be formed on nitrogen polarity surface leading to high driving voltage drop

Engineering Contradiction:

Improveelectrode material stacking processVSAvoidohmic contacting interface quality

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies different electrode material configurations to different polarity surfaces: Ti/Al stack is used on gallium polarity surface while Al/GaN/SiN is used on nitrogen polarity surface. This local differentiation resolves the contradiction by optimizing each interface for its specific polarity characteristics, achieving superior ohmic contact on nitrogen polarity surface while maintaining manufacturing feasibility.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the electrode material composition parameters based on surface polarity. By introducing GaN and SiN layers with specific properties on the nitrogen polarity surface, the electrical contact parameters are optimized to achieve low resistance ohmic contact, thereby resolving the high driving voltage drop issue while maintaining processability.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If Ti/Al electrode layer is formed on nitrogen polarity surface, then manufacturing process is simplified, but high driving voltage drop occurs and heat emission increases reducing LED lifespan

Engineering Contradiction:

Improveelectrode layer formation processVSAvoidLED lifespan

Core Design Contradiction:

Ease of manufactureVSDuration of action of moving object

Solution Approach 1:

The patent introduces a specialized Al/GaN/SiN electrode structure specifically for the nitrogen polarity surface, differentiating it from the gallium polarity surface treatment. This local optimization reduces contact resistance and heat generation at the critical nitrogen polarity interface, thereby extending LED lifespan while maintaining manufacturing efficiency.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent introduces GaN and SiN as intermediary layers between the Al electrode and the semiconductor surface on nitrogen polarity substrates. These intermediary layers facilitate better electrical contact and thermal management, resolving the lifespan reduction issue caused by direct Ti/Al contact while keeping the overall process straightforward.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If vertical-type LED structure is adopted, then device integration is improved, but superior ohmic contacting interface cannot be formed leading to high driving voltage drop

Engineering Contradiction:

Improvedevice structure integrationVSAvoidelectrical contact performance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent maintains the vertical-type LED structure for integration benefits while introducing locally optimized electrode configurations: Ti/Al on gallium polarity surface and Al/GaN/SiN on nitrogen polarity surface. This local differentiation ensures superior ohmic contact at each interface despite the vertical architecture, resolving the electrical contact performance issue.

Inventive Principle:

Principle #3Local quality

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

This configuration enhances electrical characteristics by enabling efficient current injection and reducing heat emission, thereby improving the lifespan of the LED.

Implementation Method 1

a surface modification layer on the first conductive semiconductor layer

Methodology Applied

Scientific EffectSurface modification:

Implementation Method 2

a wafer bonding layer on the support substrate

Methodology Applied

Scientific EffectWafer bonding:

Implementation Method 3

a current spreading layer on the wafer bonding layer

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS9059338B2Light emitting element and a production method therefor

Publication Date: 2015.06.16 SUZHOU LEKIN SEMICON CO LTD

AI summary

Disclosed are a light emitting device and a method of manufacturing the same. The light emitting device includes a support substrate, a wafer bonding layer on the support substrate, a current spreading layer on the wafer bonding layer, a second conductive semiconductor layer on the current spreading layer, an active layer on the second conductive semiconductor layer, a first conductive semiconductor layer on the active layer, a surface modification layer on the first conductive semiconductor layer, and a first electrode layer on the surface modification layer.