LED Subpixel Etendue Enhancement via Tapered Sidewalls
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for fabricating light emitting diode (LED) subpixels and power devices face challenges in achieving efficient light emission and electrical connectivity, particularly in forming optically active compound semiconductor layer stacks and ensuring reliable electrical isolation and light extraction.
Innovation Solution
The semiconductor structure includes a mesa base semiconductor portion with tapered sidewalls, a growth mask layer, optically active compound semiconductor layer stacks, and a dielectric liner layer, along with a reflector layer and anode contact electrodes, which are selectively grown and patterned to enhance light emission and electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If selective area growth is used to form active regions, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The semiconductor structure is divided into multiple discrete active regions formed through selective area growth, with each active region independently positioned and sized. The growth mask layer is segmented into multiple openings that define the location and geometry of each active region, enabling precise control over the spatial distribution of light-emitting elements while maintaining a modular structure that can be systematically fabricated
Solution Approach 2:
The growth mask layer is formed beforehand with precisely patterned openings that define where active regions will grow. This preliminary patterning step establishes the geometric constraints and positional accuracy for subsequent selective epitaxial growth, ensuring that active regions form only in desired locations with controlled dimensions before the actual light-emitting structures are created
2Illumination intensity
If tapered sidewalls are formed on mesa base, then light extraction is improved, but manufacturing precision requirements increase
Solution Approach 1:
The sidewalls of the mesa base structure are formed with a controlled taper angle that optimizes light extraction by redirecting emitted photons at angles that reduce total internal reflection. This geometric parameter modification changes the optical path of generated light, improving extraction efficiency while the taper dimensions are controlled through standard photolithography and etching processes rather than requiring ultra-precise manufacturing
3Illumination intensity
If multiple semiconductor layer stacks are formed, then light emission performance is improved, but ease of manufacture decreases
Solution Approach 1:
Multiple semiconductor layer stacks containing active regions are formed and electrically connected in parallel configuration. This merging of multiple light-emitting elements into a single integrated structure combines their optical output to enhance overall light emission performance while sharing common electrical connections and support infrastructure, thereby distributing the manufacturing complexity across replicated units rather than creating a uniquely complex single structure
4Reliability
If anode contact electrode continuously overlies multiple layers, then electrical connectivity is improved, but device complexity increases
Solution Approach 1:
The anode contact electrode is designed as a continuous conductive layer that simultaneously performs multiple functions: providing electrical connection to all active regions through the p-type semiconductor material, serving as a common current distribution path, and acting as an optical interface layer. This multi-functional electrode structure consolidates what would otherwise require separate connection elements into a single universal component, improving reliability while avoiding proportional increases in complexity
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 enables improved light extraction and electrical isolation, leading to enhanced performance and efficiency of LED subpixels and power devices by optimizing the semiconductor structure and growth processes.
Implementation Method 1
at least one active region located on the at least one selectively grown epitaxial semiconductor structure and including an optically active compound semiconductor layer stack configured to emit light
Implementation Method 2
a reflector layer comprising a metal and having a thickness of at least 500 nm and electrically shorted to the anode contact electrode
Data Source
AI summary
A method of forming a light emitting device includes forming a growth mask layer including openings on a doped compound semiconductor layer, forming first light emitting diode (LED) subpixels by forming a plurality of active regions and second conductivity type semiconductor material layers employing selective epitaxy processes, and transferring each first LED subpixel to a backplane. An anode contact electrode may be formed on the second conductivity type semiconductor material layers for redundancy. The doped compound semiconductor layer may be patterned with tapered sidewalls to enhance etendue. An optically clear encapsulation matrix may be formed on the doped compound semiconductor material layer to enhance etendue. Lift-off processes may be employed for the active regions. Cracking of the LEDs may be suppressed employing a thick reflector layer.