GaN LED With Segmented Substrate To Reduce Crystal Defects
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Solution Overview
Problem
Conventional gallium nitride-based light emitting diodes (LEDs) face reduced internal quantum efficiency and performance due to crystal defects in the semiconductor structure, which are exacerbated by the lattice mismatch and thermal expansion differences between sapphire substrates and GaN epitaxial layers, leading to nonradiative recombination and heat production.
Innovation Solution
A substrate with alternating first grooves and convex parts is used, with a semiconductor structure featuring corresponding second convex and grooves, and a transparent conductive layer configured to direct current through the parts with fewer crystal defects, reducing nonradiative recombinations and enhancing light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flat sapphire substrate is used for growing GaN epitaxial layer, then the substrate provides a conventional platform for hetero-epitaxy, but lattice mismatch and thermal expansion differences cause crystal defects and nonradiative recombination centers
Solution Approach 1:
The substrate surface is segmented into convex parts and grooves, creating a non-uniform topography that divides the growth area into regions with different defect densities. The semiconductor structure is grown selectively on convex parts, isolating defect propagation and preventing nonradiative recombination across the entire device area.
Solution Approach 2:
Different regions of the substrate surface are given different properties: convex parts provide elevated growth sites with reduced defect density, while grooves act as isolation barriers. This local differentiation ensures that critical light-emitting regions have optimal crystal quality while maintaining overall device manufacturability.
2Productivity
If current flows through the entire semiconductor structure, then the device utilizes the full active area, but current passing through crystal defects increases nonradiative recombination and heat production
Solution Approach 1:
The current path is segmented into multiple parallel channels, each confined to a convex region. This segmentation ensures that current flows through discrete, defect-minimized areas rather than traversing the entire structure including defect-prone groove regions, reducing nonradiative recombination while maintaining total light output.
Solution Approach 2:
The grooves, which would normally be considered defective or wasted areas, are strategically used to isolate and contain current flow paths. By directing current away from groove regions and concentrating it on convex parts, the design converts potentially harmful defect zones into beneficial current-guiding features that reduce energy loss.
3Device complexity
If the semiconductor structure is formed on a flat substrate, then the fabrication process is simplified, but crystal defects are increased in the semiconductor structure
Solution Approach 1:
The substrate surface is pre-patterned with convex parts and grooves before epitaxial growth. This preliminary structuring creates predetermined high-quality growth sites that guide crystal formation, ensuring low defect density in the semiconductor structure without requiring complex in-situ control during the growth process itself.
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 design significantly increases internal quantum efficiency by minimizing current flow through defect-prone areas, improving energy utilization and light emission efficiency, while also enhancing external quantum efficiency through controlled current flow and light refraction.
Implementation Method 1
a transparent conductive layer formed on the semiconductor structure and configured to transmit a current to the plurality of second convex parts
Implementation Method 2
a light emitting layer 22 formed on the n-type gallium nitride layer 21... the light emitting layer 22 may generate and emit light
Data Source
AI summary
A light emitting diode includes a substrate comprising a plurality of first grooves and a plurality of first convex parts formed on a surface of the substrate, with the first groove formed between two neighboring first convex parts; a semiconductor structure formed on the substrate comprising a plurality of second convex parts corresponding to the plurality of first grooves and a plurality of second grooves corresponding to the plurality of first convex parts; a transparent conductive layer formed on the semiconductor structure and configured to transmit a current to the plurality of second convex parts; a first electrode electrically connected with the semiconductor structure; and a second electrode electrically connected with the transparent conductive layer. A method for preparing the light emitting diode is also provided.