Top-Emitting N-Based LED Transparent Conductive Film Patterning

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Solution Overview

Problem

Conventional methods for forming high-quality ohmic contacts in N-based light emitting devices, such as Ni/Au and Ni/ITO, face challenges with low light extraction rates due to the need for additional processing steps like dry-etching and micro-scale patterning, which can damage electrodes and limit light output, especially for wavelengths between 400 to 500 nm.

Innovation Solution

A method involving nano-scale patterning of a transparent conductive thin film using wet-etching and annealing without a mask, forming a p-type ohmic electrode with improved light extraction by diffusing reflection at the interface, using transparent conductive oxides like In, Sn, or Zn, and potentially adding dopants for enhanced conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional Ni/Au or Ni/ITO ohmic contact structures are used, then electrical conductivity is improved, but light extraction rate deteriorates due to low light transmittance

Engineering Contradiction:

Improveelectrical conductivityVSAvoidlight extraction rate

Core Design Contradiction:

ReliabilityVSIllumination intensity

Solution Approach 1:

The patent changes the physical and chemical parameters of the transparent conductive oxide thin film through controlled wet-etching and thermal annealing processes. The etching creates nanoscale surface roughness while annealing restores conductivity by redistributing metal atoms, achieving both high light extraction and electrical performance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite structures combining transparent conductive oxides (ITO, IZO, IGZO) with metal layers (Ni, Au) in specific configurations. The composite structure leverages the high transmittance of TCO and the excellent conductivity of metals to achieve both optical and electrical requirements

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If dry-etching and micro-scale patterning are used to improve light extraction, then light output is improved, but electrode damage occurs and manufacturing complexity increases

Engineering Contradiction:

Improvelight outputVSAvoidelectrode damage

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the mechanical dry-etching process with a chemical wet-etching process followed by thermal annealing. This substitution eliminates plasma damage to the electrode while achieving the desired nanoscale surface roughness for enhanced light extraction through diffraction and scattering effects

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent converts the potential harm of over-etching into a benefit by controlling the etching process to create optimal nanoscale roughness, then using annealing to restore conductivity. The controlled damage from etching becomes the foundation for enhanced light extraction when combined with the recovery effect of annealing

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Ease of manufacture

If micro-meter sized hole patterns are used for texturing, then manufacturing is simplified, but light extraction rate for 400-500 nm wavelength deteriorates

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidlight extraction rate

Core Design Contradiction:

Ease of manufactureVSIllumination intensity

Solution Approach 1:

The patent transitions from micro-meter scale (2D) patterning to nanoscale (3D surface topology) roughness modification. The wet-etching and annealing process creates complex nanoscale surface features that are effective for blue light extraction without requiring large-scale geometric patterns, thus maintaining manufacturing simplicity while improving optical performance

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 approach increases the light extraction rate and improves electrical characteristics by maintaining consistent sheet resistance and reducing reverse currents, resulting in higher light output power and better optical performance compared to conventional methods.

Implementation Method 1

wet-etching the transparent conductive thin film

Methodology Applied

Scientific EffectWet-etching:

Implementation Method 2

annealing the wet-etched transparent conductive thin film

Methodology Applied

Scientific EffectAnnealing: Annealing

Implementation Method 3

inducing a diffused reflection of light generated in the light emitting device at an interface by nano-scale patterning

Methodology Applied

Scientific EffectDiffused reflection: Reflection

Data Source

PatentUS8227283B2Top-emitting N-based light emitting device and method of manufacturing the same

Publication Date: 2012.07.24 SAMSUNG ELECTRONICS CO LTD

AI summary

Provided is a top-emitting N-based light emitting device and a method of manufacturing the same. The N-based light emitting device may include an n-type clad layer, an active layer, a p-type clad layer, and a transparent conductive thin film which may be sequentially stacked on a substrate. The transparent conductive thin film may have a surface nano-scale patterned by wet-etching and then annealing without using a mask for improving the light extraction rate. A light emitting device having a higher brightness may be prepared by increasing or maximizing the light extraction rate by employing the transparent conductive thin film having the surface patterned by wet-etching and then annealing.