Resonant-Cavity Micro-LED Structure for Narrow Emission Angles
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Solution Overview
Problem
Conventional micro-LEDs suffer from large emission angles, thermal instability due to red shift, and low luminous efficiency, which affect their performance in applications requiring collimated light emission and high brightness, such as virtual/augmented reality glasses and battery-powered consumer electronics.
Innovation Solution
A micro-LED structure with a resonant cavity is developed, comprising a substrate, a first reflector layer, an LED unit, and a second reflector layer, where the LED unit is surrounded by an ion-implanted isolation material to form an optical cavity, enhancing light directionality and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional micro-LEDs are used, then the device size is small, but the emission angle is large and light directionality is poor
Solution Approach 1:
The patent segments the micro-LED structure into distinct functional layers including a resonant cavity with distributed Bragg reflectors (DBRs) at the bottom and a microlens array at the top. This segmentation allows each layer to perform its specific function: the resonant cavity confines and directs light vertically, while the microlens array further focuses the emitted light, achieving narrow emission angles and improved directionality without increasing device size.
Solution Approach 2:
The patent introduces vertical dimensionality through the resonant cavity structure with multiple DBR layers stacked beneath the active region. This vertical stacking creates optical confinement in the vertical dimension, directing light emission primarily in the vertical direction and reducing lateral emission, thereby achieving narrow emission angles and improved light directionality.
2Device complexity
If conventional micro-LEDs are used, then the device structure is simple, but the luminous efficiency is low
Solution Approach 1:
The patent segments the micro-LED into functionally distinct layers including n-type DBRs, p-type DBRs, active regions, and microlens elements. This segmentation optimizes light extraction and confinement in each layer, reducing internal reflections and improving overall luminous efficiency. The segmented structure enables better management of optical paths and reduces energy loss despite increased structural complexity.
Solution Approach 2:
The patent employs composite material structures combining semiconductor layers with different bandgaps, metallic reflector layers, and dielectric microlens materials. These composite materials work together to enhance light emission, confinement, and extraction efficiency, improving luminous efficiency by leveraging the complementary optical properties of different materials in a integrated structure.
3Ease of manufacture
If conventional micro-LEDs are used, then the manufacturing process is simple, but the spectral stability is poor due to red shift
Solution Approach 1:
The patent segments the micro-LED structure into temperature-compensated layers with different thermal expansion coefficients and bandgap characteristics. The resonant cavity is designed with specific layer thicknesses and materials that compensate for thermal-induced wavelength shifts, maintaining spectral stability during operation despite manufacturing simplicity.
Solution Approach 2:
The patent optimizes parameters such as layer thickness, refractive index, and bandgap energy of the resonant cavity layers to achieve thermal compensation. By carefully selecting and tuning these parameters, the structure compensates for thermal effects that cause red shift, maintaining stable peak wavelength across operating temperatures while keeping the manufacturing process relatively simple.
4Volume of moving object
If conventional micro-LEDs are used, then the device is compact, but the light extraction efficiency is low
Solution Approach 1:
The patent segments the micro-LED into a resonant cavity structure with multiple DBR layers and an active region, creating optical confinement that enhances light extraction. The segmented structure allows light to be confined and redirected multiple times within the compact volume, increasing extraction efficiency without requiring a larger device size.
Solution Approach 2:
The patent utilizes the vertical dimension by stacking DBR layers and creating a resonant cavity structure beneath the active region. This vertical stacking enables optical confinement and multiple light extraction opportunities within a compact footprint, improving light extraction efficiency without increasing lateral device dimensions.
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 resonant cavity design improves light directionality, reduces red shift, and increases external quantum efficiency, resulting in superior spectral purity and brightness stability.
Implementation Method 1
The first reflector layer, the LED unit and the second reflector layer are configured to collectively provide a resonant cavity
Implementation Method 2
The first reflector layer, the LED unit and the second reflector layer are configured to collectively provide a resonant cavity
Implementation Method 3
a first reflector layer formed between the substrate and the LED unit, and a second reflector layer formed on the LED unit
Implementation Method 4
An implantation operation is performed to form an isolation material surrounding at least one optical cavity in the semiconductor structure
Data Source
AI summary
Methods for manufacturing a light emitting diode (LED) structure. One exemplary method includes forming a first reflector layer and a semiconductor structure on a first substrate, performing an implantation operation to form an isolation material surrounding at least one optical cavity unit in the semiconductor structure, forming a passivation layer on the semiconductor structure, forming an electrode layer on the passivation layer, and forming a second reflector layer on the passivation layer and the electrode layer.