GaN Light-Emitting Structure With Masked Openings for Dislocation Control
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Solution Overview
Problem
GaN-based light-emitting devices face challenges with high dislocation density, which hinders their efficiency, and existing epitaxial growth methods on Al2O3 substrates result in dislocation surface densities of 1~3E8/cm3, limiting their performance.
Innovation Solution
A light-emitting device structure featuring a substrate with an oblique columnar opening in a mask layer, where the first opening's geometry and angle help terminate dislocations, combined with epitaxial growth techniques like MOCVD, ALD, or CVD, to reduce dislocation density and enhance light-emitting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional epitaxial growth methods on Al2O3 substrates are used, then the manufacturing process is simple, but the dislocation density is high (1-3E8/cm3)
Solution Approach 1:
The mask layer is divided into multiple openings with different cross-sectional areas, creating segmented growth regions. Each opening serves as an independent epitaxial growth chamber, allowing dislocations to be confined and terminated at the sidewalls of individual openings, thereby reducing overall dislocation density in the GaN layer
Solution Approach 2:
The invention transitions from planar epitaxial growth to three-dimensional growth within openings. By creating openings with specific depth-to-width ratios and varying cross-sectional areas, the patent utilizes the vertical dimension to extend sidewall surface area, providing additional dislocation termination pathways and reducing dislocation propagation
2Manufacturing precision
If the open end area of the first opening is made smaller than the substrate area, then dislocation termination is improved, but the light-emitting area is reduced
Solution Approach 1:
Multiple openings are arranged on the substrate, each with controlled cross-sectional area. The segmentation allows dislocation termination at sidewalls while distributing the light-emitting function across multiple structures, effectively balancing dislocation reduction with maintained light-emitting area
Solution Approach 2:
The light-emitting structure is nested within the openings of the mask layer. This nesting arrangement allows the active light-emitting region to be positioned within the confined space of each opening, maximizing light emission from the narrowed cross-sectional area while maintaining effective dislocation termination at the opening sidewalls
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 proposed structure effectively reduces dislocation density and improves light-emitting efficiency by increasing the area of the sidewall that terminates dislocation extension, resulting in higher quality GaN-based light-emitting devices with improved brightness and wavelength control.
Implementation Method 1
a refractive index of the plurality of first sub-layers being different with a refractive index of the plurality of second sub-layers to form a Bragg reflector, and the Bragg reflector makes a light emitted by the light-emitting structure exit in a direction, perpendicular to the plane where the substrate is located
Implementation Method 2
the first mask layer includes a metal reflective layer, and an orthographic projection of the light-emitting structure on the plane where the substrate is located overlaps with at least a part of an orthographic projection of the metal reflective layer on the plane where the substrate is located, and the metal reflective layer makes the light emitted by the light-emitting structure exit in a direction, perpendicular to the plane where the substrate is located
Implementation Method 3
a first epitaxial layer epitaxially grown in the first opening on the substrate; and a light-emitting structure epitaxially grown in the first opening on the first epitaxial layer
Data Source
AI summary
A light-emitting device includes: a substrate; a first mask layer, a first epitaxial layer and a light-emitting structure. The first mask layer is arranged on the substrate and includes a first opening exposing the substrate, the first opening includes an open end, an area of an orthographic projection of the open end on a plane where the substrate is located is smaller than an area of an orthographic projection of the first opening on the plane where the substrate is located; the first epitaxial layer is epitaxially grown in the first opening on the substrate to fill up the first opening; and the light-emitting structure is arranged on the first epitaxial layer and on the first mask layer. An inward sidewall of the first opening is utilized to terminate dislocations of GaN-based material, thereby reducing a dislocation density of the GaN-based material and improving a light-emitting efficiency.