Vertical LED Sidewall Passivation for Micro LED Efficiency

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Micro LEDs face efficiency degradation due to non-radiative recombination at the sidewalls, which is exacerbated by unsatisfied bonds, chemical contamination, and structural damage, leading to reduced luminous efficacy, especially at low current densities.

Innovation Solution

Implementing sidewall passivation techniques such as in-situ etching and regrowth, diffusion, and current confinement structures to minimize defects and move the active layer edges interiorly within the p-n diode layer, reducing lateral carrier diffusion and surface recombination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If micro LEDs are operated at low current densities, then power consumption is reduced, but efficiency deteriorates due to strong non-radiative recombination effects

Engineering Contradiction:

Improvepower consumptionVSAvoidnon-radiative recombination loss

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The patent applies local quality by creating a passivation layer specifically at the sidewalls where non-radiative recombination occurs. This localized treatment addresses the specific problem area (sidewall defects) without changing the entire LED structure, allowing low current operation with maintained efficiency by reducing surface recombination velocity at the passivated regions

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The passivation layer acts as an intermediary between the defective sidewall surface and the active region. This intermediate layer reduces the harmful interaction between carriers and surface defects, enabling efficient radiative recombination even at low injection currents where non-radiative effects would normally dominate

Inventive Principle:

Principle #24Intermediary (Mediator)

2Area of stationary object

If the active layer edges are positioned closer to the sidewalls, then device area is reduced, but efficiency deteriorates due to increased surface recombination

Engineering Contradiction:

Improvedevice areaVSAvoidsurface recombination loss

Core Design Contradiction:

Area of stationary objectVSLoss of energy

Solution Approach 1:

The patent applies local quality by creating a passivation layer specifically at the sidewalls where non-radiative recombination occurs. This localized treatment addresses the specific problem area (sidewall defects) without changing the entire LED structure, allowing compact design with maintained efficiency by reducing surface recombination velocity at the passivated regions

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The passivation layer acts as an intermediary between the defective sidewall surface and the active region. This intermediate layer reduces the harmful interaction between carriers and surface defects, enabling efficient radiative recombination even when active layer edges are close to sidewalls, thus allowing smaller device area without efficiency penalty

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of energy

If sidewall passivation is implemented, then radiative efficiency is improved, but device complexity increases

Engineering Contradiction:

Improveradiative efficiencyVSAvoidstructure complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent applies parameter changes by modifying the electrical properties of the sidewall region through passivation. This changes the surface recombination velocity parameter from high (defective) to low (passivated), improving radiative efficiency without fundamentally changing the LED's basic structure or requiring complex additional components

Inventive Principle:

Principle #35Parameter changes

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

Enhances radiative efficiency by minimizing non-radiative recombination, preserving the lattice structure, and confining current injection internally, thereby improving the overall efficiency of micro LEDs.

Implementation Method 1

sidewall passivation techniques such as in-situ etching and regrowth, diffusion

Methodology Applied

Scientific EffectSurface passivation:

Implementation Method 2

in-situ etching and regrowth

Methodology Applied

Scientific EffectIn-situ etching and regrowth:

Implementation Method 3

diffusion

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS9601659B2LED structures for reduced non-radiative sidewall recombination

Publication Date: 2017.03.21 APPLE INC

AI summary

LED structures are disclosed to reduce non-radiative sidewall recombination along sidewalls of vertical LEDs including p-n diode sidewalls that span a top current spreading layer, bottom current spreading layer, and active layer between the top current spreading layer and bottom current spreading layer.