GaN MicroLED Fabrication With Self-Aligned Ohmic Contact Etching
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Solution Overview
Problem
GaN-based LED devices face challenges such as poor alignment during fabrication, leading to reduced yield and inefficient light extraction due to deep trenches and multi-layers, which worsen with increased device size, and result in decreased external efficiency.
Innovation Solution
A method for fabricating a microLED array that combines the formation of ohmic contacts and etch mask layers, using a beryllium species implanted into gallium and nitrogen containing materials to form low resistivity materials, and a self-aligned etching process to reduce alignment errors and trench depth, enabling improved electrical characteristics and light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional multi-step fabrication processes are used with deep trenches and multiple etch mask layers, then device functionality is achieved, but alignment errors increase and manufacturing precision deteriorates
Solution Approach 1:
The patent combines the formation of ohmic contacts and etch mask layers into a single integrated structure. The beryllium-doped GaN layer serves dual purposes: as the ohmic contact region and as the etch mask layer, eliminating the need for separate mask deposition and alignment steps. This merging of functions directly reduces alignment errors and simplifies the fabrication process.
Solution Approach 2:
The beryllium-doped GaN layer performs multiple functions simultaneously: it provides ohmic contact functionality for electrical connection, serves as an etch mask for defining device patterns, and acts as a protective layer during processing. This multi-functionality eliminates the need for separate dedicated mask layers, reducing the number of processing steps and alignment requirements.
2Ease of manufacture
If deep trenches and multi-layers are used in LED structure, then device functionality is achieved, but light extraction efficiency decreases
Solution Approach 1:
The patent extracts and eliminates the deep trench structure from the LED device design. By using the beryllium-doped GaN layer as both ohmic contact and etch mask, the need for deep trenches is removed. This extraction of the problematic deep trench structure directly improves light extraction efficiency while maintaining device functionality through the alternative contact and masking approach.
3Productivity
If increased device size is implemented, then pixel density is improved, but alignment errors worsen and yield decreases
Solution Approach 1:
The patent merges the ohmic contact formation and etch mask definition into a single simultaneous process step using the beryllium-doped GaN layer. This eliminates sequential alignment steps that would compound errors in larger devices. By performing both functions in one step, the patent enables increased device size and pixel density without the penalty of accumulated alignment errors.
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 significantly reduces alignment errors, increases yield, and enhances light extraction efficiency by simplifying the fabrication process and reducing the number of processing steps, resulting in higher pixel density and larger device sizes with greater than 99.5% electrical yield.
Implementation Method 1
uses a beryllium species configured with implantation techniques into a crystalline gallium and nitrogen containing material to form a low resistivity material
Data Source
AI summary
Light Emitting Diodes (LEDs) made with GaN and related materials are used to realize high efficiency devices which emit visible radiation. These GaN-based LEDs consists of a multi-layer structure which include p-type electron confinement layers, and p-type current spreading and ohmic contacts layers located above the active region. The alignment of the etched features which penetrate near or through the active region and the ohmic contact is critical and is currently a technological challenge in the fabrication process. Any errors in this alignment and successive layers will short across the active layers of the device and result in reduced yield of functional devices. The invention described herein provides a method and apparatus to realize the successful alignment and streamlined fabrication of high-density LED array devices. The result is a higher pixel density GaN-based LED device with higher current handling capability resulting in a brighter device of the same area.