Ohmic Electrode Structure for Nitride Semiconductor Light Emitting Elements

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Nitride semiconductor light emitting elements face challenges in achieving high power and thermal stability due to issues with electrode materials, such as high contact resistance with Al and poor interlayer adhesive strength and thermal stability of Ag, limiting their efficiency and increasing fabrication costs.

Innovation Solution

A method of forming an ohmic electrode with a reflective layer of Ag or Al, a bonding layer to reduce contact resistance, and a protective layer to enhance thermal stability, involving a heat treatment process to form oxide films, which suppresses external diffusion and maintains high reflectivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If Al is used as electrode material, then light reflectivity is improved, but contact resistance with nitride-based semiconductor layer increases

Engineering Contradiction:

Improvelight reflectivityVSAvoidcontact resistance

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent employs a composite electrode structure consisting of multiple layers including Al or Ag reflective layer, barrier layer, and adhesion layer. This composite structure combines materials with different properties: Al/Ag for high reflectivity, barrier layer for diffusion prevention, and adhesion layer for low contact resistance and strong bonding to the nitride-based semiconductor layer.

Inventive Principle:

Principle #40Composite materials

2Reliability

If Ag is used as electrode material, then contact resistance is reduced, but interlayer adhesive strength and thermal stability deteriorate

Engineering Contradiction:

Improvecontact resistanceVSAvoidinterlayer adhesive strength

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The electrode structure uses a composite design where Ag is combined with barrier and adhesion layers. The barrier layer prevents diffusion and maintains thermal stability, while the adhesion layer ensures strong interlayer bonding. This composite approach retains Ag's low contact resistance while compensating for its poor adhesion and thermal stability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The barrier layer and adhesion layer serve as intermediary layers between the Ag reflective layer and the semiconductor layer. These intermediary layers mediate the interface properties, preventing direct contact between Ag and the semiconductor, thus avoiding diffusion issues while maintaining electrical contact and mechanical adhesion.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If Au or Pt is used as electrode material, then contact resistance and thermal stability are improved, but fabrication cost increases

Engineering Contradiction:

Improvecontact resistanceVSAvoidfabrication cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces expensive Au or Pt materials with cheaper Al or Ag materials for the reflective layer. By using the composite structure with barrier and adhesion layers, the cheaper materials achieve comparable reliability in terms of contact resistance and thermal stability, thus significantly reducing fabrication cost while maintaining performance.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 enables high power light emission with low contact resistance, improved thermal stability, and reduced fabrication costs by using Ag or Al electrodes with a bonding and protective layer structure, enhancing light availability and operational reliability.

Implementation Method 1

performing a heat treatment process to form ohmic bonding between the semiconductor layer and the bonding layer and to form an oxide film on at least a portion of the protective layer

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Implementation Method 2

form an oxide film on at least a portion of the protective layer

Methodology Applied

Scientific EffectOxidation: Oxidation

Implementation Method 3

a reflective layer is formed of Ag or Al with excellent light reflectivity

Methodology Applied

Scientific EffectLight reflection: Reflection

Implementation Method 4

performing a heat treatment process to form ohmic bonding between the semiconductor layer and the bonding layer

Methodology Applied

Scientific EffectOhmic bonding:

Data Source

PatentUS8921885B2Method for forming ohmic electrode and semiconductor light emitting element

Publication Date: 2014.12.30 SEOUL VIOSYS CO LTD

AI summary

The present invention relates to a method of forming an ohmic electrode in a semiconductor light emitting element, comprising: forming a semiconductor layer having a light emitting structure on a substrate, sequentially laminating a bonding layer, a reflective layer and a protective layer on the semiconductor layer, and forming an ohmic electrode by performing a heat treatment process to form ohmic bonding between the semiconductor layer and the bonding layer and to form an oxide film on at least a portion of the protective layer; and a semiconductor light emitting element using the ohmic electrode. According to the present invention, since a reflective layer is formed of Ag, Al and an alloy thereof with excellent light reflectivity, the light availability is enhanced. Further, since contact resistance between a semiconductor layer and a bonding layer is small, it is easy to apply large current for high power.