LED Array Pitch Reduction via Reflector-Mediated Electrical Isolation
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Solution Overview
Problem
Current LED technologies face challenges in minimizing the pitch between adjacent LEDs in arrays, which affects the resolution and brightness of display systems, particularly in high-resolution micro-LED displays used in artificial reality systems.
Innovation Solution
The solution involves forming an array of LEDs with a reflector in Ohmic contact with adjacent LEDs, where the reflector is physically separated from the p-contact, and an n-contact is formed at the interface between the reflector and the n-type layer, allowing for a pitch of less than or equal to 1.8 μm, and using a conical mesa shape for each LED with a metallic mesh for individual addressing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the pitch between adjacent LEDs is reduced to increase packing density and resolution, then the resolution and brightness of the display system is improved, but the electrical isolation between adjacent LEDs becomes more difficult to maintain
Solution Approach 1:
A reflector structure is introduced as an intermediary element that serves dual functions: it provides optical reflection to enhance light extraction efficiency, and simultaneously acts as an electrical isolation barrier between adjacent LEDs through Ohmic contact with n-type layers. This mediator allows the LEDs to be packed closer together while maintaining electrical isolation, resolving the contradiction between reduced pitch and reliable electrical isolation.
Solution Approach 2:
The reflector is designed to perform multiple functions simultaneously: (1) optical reflection to improve light extraction, (2) electrical isolation between adjacent LEDs through Ohmic contact with n-type layers, and (3) structural support for the LED array. This multi-functionality allows a single structure to address both the resolution improvement goal and the electrical isolation requirement, eliminating the need for separate isolation structures that would increase pitch.
2Manufacturing precision
If the pitch between LEDs is reduced to less than or equal to 1.8 μm to increase packing density, then the resolution of the display system is improved, but the complexity of forming electrical contacts increases
Solution Approach 1:
The electrical contact structure is merged with the reflector structure. The reflector is formed in direct Ohmic contact with the n-type layers of adjacent LEDs, eliminating the need for separate contact structures. This merging reduces device complexity while enabling ultra-fine pitch spacing of ≤1.8 μm, as the same structure serves both optical and electrical functions.
Solution Approach 2:
The electrical contact is transitioned from a lateral configuration to a vertical configuration through the reflector structure. Instead of requiring lateral contacts between adjacent LEDs at the same plane, the reflector provides vertical Ohmic contact paths through the n-type layers, enabling closer packing in the lateral dimension while maintaining electrical connectivity in the vertical dimension.
3Manufacturing precision
If the pitch between LEDs is reduced to increase packing density, then the brightness of the display system is improved, but the light extraction efficiency between adjacent LEDs becomes more challenging
Solution Approach 1:
The reflector acts as an optical intermediary that redirects light that would otherwise be trapped or absorbed by adjacent LEDs. By providing a reflective surface in Ohmic contact with the n-type layers, the reflector redirects light extraction paths, maintaining high light extraction efficiency even when LEDs are packed at ultra-fine pitch distances of ≤1.8 μm.
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 configuration enables a significant reduction in the pitch between LEDs, enhancing the resolution and brightness of micro-LED displays, particularly in artificial reality systems, by allowing for closer packing without electrical conduction between p and n contacts, thereby improving display performance.
Implementation Method 1
a reflector that is in Ohmic contact with at least two adjacent LEDs of the plurality of LEDs
Implementation Method 2
Light emitting diodes (LEDs) convert electrical energy into optical energy
Data Source
AI summary
Disclosed herein are techniques for reducing the pitch between light-emitting diodes (LEDs) in an array of LEDs. According to an aspect of the invention, a method includes forming a plurality of stacks of layers on a surface of a semiconductor, with a p contact at an interface between each stack and a p-type layer of the semiconductor. The semiconductor is etched to form a plurality of mesa shapes corresponding to the plurality of stacks. A dielectric is formed on at least a portion of each mesa shape and at least a portion of each stack. A reflector is formed on at least a portion of the dielectric and at least a portion of the semiconductor to provide an n contact at an interface between the reflector and an n-type layer of the semiconductor. The reflector is physically separated from the p contact for each stack.