Micro-LED Narrowband Reflector for Low Ambient Reflection
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Solution Overview
Problem
Micro-LED arrays face challenges in reducing ambient light reflection, leading to reduced contrast in display performance, particularly in high-density displays where micro-LEDs occupy a significant portion of the area and have a highly reflecting backside.
Innovation Solution
Implementing a narrow-band photonic filter as a bottom reflector in micro-LEDs that preferentially reflects the emission wavelength and absorbs other wavelengths, combined with a multilayer semiconductor stack and a distributed Bragg reflector to enhance light emission efficiency and reduce ambient reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a highly reflecting backside is used in micro-LEDs, then light extraction efficiency is improved, but ambient light reflection increases reducing display contrast
Solution Approach 1:
The patent applies local quality by making the reflector wavelength-selective: it has high reflectivity at the micro-LED emission wavelength to improve light extraction, while having low reflectivity (high absorption) at ambient light wavelengths to reduce glare. This localized optimization of reflective properties at specific wavelengths resolves the contradiction between improving LED efficiency and reducing ambient reflection.
Solution Approach 2:
The patent changes the optical parameters of the reflector by using a distributed Bragg reflector design with specific layer thicknesses and refractive indices. The quarter-wavelength thickness of alternating high and low refractive index layers creates constructive interference at the emission wavelength for high reflection, while destructive interference at other wavelengths reduces ambient light reflection, thus resolving the contradiction.
2Measurement precision
If micro-LEDs are arranged in high-density arrays, then display resolution is improved, but the reflecting backside occupies significant area increasing overall reflection
Solution Approach 1:
The wavelength-selective reflector provides local quality optimization where each micro-LED pixel has high reflectivity only at its specific emission wavelength, allowing high-density packing without cumulative ambient reflection problems. The harmful broad-spectrum ambient reflection is suppressed while the useful narrow-band LED light is enhanced.
Solution Approach 2:
The patent uses color-selective optical properties where the reflector appears colored (wavelength-specific) rather than uniformly reflective. The distributed Bragg reflector is designed to reflect specific color wavelengths corresponding to the micro-LED emission while absorbing other wavelengths, reducing the overall ambient reflection in high-density displays.
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 significantly reduces ambient reflection, enhancing the contrast and efficiency of micro-LED displays by preferentially reflecting the desired wavelength while absorbing others, thereby improving display performance.
Implementation Method 1
a distributed Bragg reflector to enhance light emission efficiency and reduce ambient reflection
Implementation Method 2
a multilayer reflector structure that includes a narrowband reflector configured to have a maximum reflectance at the predetermined visible wavelength range
Implementation Method 3
a narrow-band photonic filter as a bottom reflector in micro-LEDs that preferentially reflects the emission wavelength and absorbs other wavelengths
Data Source
AI summary
A structure and method of micro-LEDs are described. The micro-LEDs have a GaN semiconductor structure containing a multi-quantum well active region configured to emit light of a visible wavelength range and a multilayer reflector structure that includes a distributed Bragg reflector (DBR) with a maximum reflectance at the visible wavelength range and to reflect the light emitted by the active region towards an emission surface of the semiconductor structure. The multilayer reflector structure also has a protective layer between the DBR and the GaN structure that is transparent to light of visible wavelengths. The multilayer reflector structure also has an absorbing metal layer that absorbs the light of visible wavelengths. A conductive material provides electrically contact to the semiconductor structure.